Repair Unallocated Space from USB Flash Drive

Often when you are into using some ‘special’ software that enables you to do fancy things on your desktop, your most trusty device is that USB Thumb Drive. With its huge storage capacity, no wonder people are using it as a boot device! Some of us might have used that to run Google OS or to load Operating Systems unto tiny Netbooks. The problem comes after we have written the image unto the Drive, only to find that there is no way to retrieve the unallocated space left by the written image. In my case, I was using the NetbookInstaller for Mac OS X, which only took 50MB out of the 3.75GB storage on my thumb drive. Naturally, right clicking on it would not allow you to recover anything (whether through ‘formatting’ or ‘property changes’). After struggling for some time, I found the answer:

0. Download the Lexar tool and extract to your PC – Click here to download:
1. On Windows 7, remember to right click and “Run as Admin”.
2. Select your thumb drive letter, and click on the ‘Non-Active’ radio button at the bottom of the window
3. Now click on the ‘Format’ button
4. Remove and insert back of your Flash drive
5. Go back to disc management and reformat the flash drive again and you will get the whole space again


Update: 10/3/2011

Thanks to Chrno for this tip:

“One problem though was BootIt crashing while formating even with admin [privileges]. Seems running it in compatibility mode for XP did the trick.”

You can do this by right-clicking BootIt and choosing “Properties” and going to the “Compatibility” tab, tick the box on “Compatibility mode” Run this program for: Windows XP…



202 thoughts on “Repair Unallocated Space from USB Flash Drive

  1. Pingback: Hello Heavy-Duty Samsung ML 1620 Printer, Meet Heavy My Task Sheet | Which Web Hosting

      • This process can help u with out doing all above things:
        Step 1: Run -> CommandPrompt ->
        Step 2: Type diskpart ->Enter
        Step 3: Type list disk ->Enter
        Note: (Find out the allocated number of your disk)
        Step 4: Type select disk X ->Enter
        Note: (If X is the number for your drive)
        Step 5: Type clean ->Enter
        Note: (If you want to create partition in desired disk continue next step, otherwise ignore it.)
        Step 6: Type create partition primary ->Enter

      • Many thanks for that. I was unable to recover 3.8gb unallocated space from my pendrive using your advice

      • wow, this is amazing. something so simply and it worked. great job and thank-you!! 🙂

      • Thank you Anatha! I have been trying for months to get the unallocated space back. I have tried all kinds of software and various methods but had forgotten about diskpart. Thanks!

  2. THANK YOU!! Put ChromeOS on it many months ago but needed to use it as storage today and could not get anything to work or any answers until I found this post.

  3. Pingback: URGENT need help formating a 8gb flash drive - -

  4. Pingback: URGENT need help formating a 8gb flash drive - -

  5. Thanks a lot! I was very tense after getting only 949 MB in my pen drive after putting Chrome OS on it. using all tools i couldn’t get all the space. I got it in just a few seconds with it.

  6. Thank you very very very much! Just spent half an hour with lexar support and they couldn’t help. Your post sorted it in 2 minutes! – Thanks again!

  7. Thank youuuuuuuuuu!!!

    I actually threw once of my USB sticks away because i couldn’t find a way to fix it, but this helped me fix my dad’s USB stick which I broke by reformatting it. Apparently my mac likes to screw it up every time I format a USB stick =/

  8. I searched all over the place for a way to recover my Lexar thumb drive. I had given up hope and was just thinking a reformat would do the trick. Instead, this tool completely recovered my drive and all the data. Thanks very much.

  9. I had installed VMWare ESXi on the pen-drive and later when need, showed only 4GB of 8GB.
    Tried all and reventually got the drive to just 8MB.
    Now using these instructions, I am back in business, got all of the 8GB available.
    God Bless…

  10. Didn’t work for me. I ran the program as admin, but it always ended up giving me the following error: “Cannot find file data”

    Nevertheless, I found a better solution. My MAC disk utility fixed it in a blink

    • Thank you so much for your help, I was at my wits end trying to figure out what to do.
      Really appreciate your time & effort to post with Mac-specific help.


  12. Thanks so much! I just bought a 4gb usb today and was experimenting with it. Reformatted it after writing an image to it and it was at 250mb! This was just what I needed.

  13. Dude, this worked excellent. I’ve been trying out Linux Distro’s on my thumb drives and it turned an 8 gig drive into a 450mb drive.

    This processed worked perfectly!!!!

    Thanx again, GWDavis28 |B)

  14. i freaking forgot i had chrome OS on my flashdrive! i was like what is this Unallocated space s* that i cannot format normally.. you helping me out a ton. thank you!

  15. i have a usb that can not be format by the window and i tried the software bootlt v1.07 to format however the this software did’nt detect the dirve (G):,, do you a any coment about this or a suggestion that i can recover my 8GB flash drive

  16. I have 4 GB kingston USB, but problem is that the USB Cannot be formated and also show disk space 8 MB because USB accurate space is 4 Gb.

    So plz how i sole this problem.

  17. OMG!!!This is not possible looool

    Very tnx mate, it works perfectly.

    U are so pro, not everyone can make program like this!!

    All the best buddy!

  18. Heyy thanks dude, I nearly went to buy a new one and was really heart broken, i had an 8 GB usb stick (shrunk to 1GB) thaT my sweet sister gifted me. …Thanks a lot …cheers!!

  19. Thank you SO MUCH! It is crazy, I had used my Lexar Jumpdrive for NetbookInstaller… such a coincidence that this software to fix the problem was from Lexar, just what I needed.

  20. Thank you so much.I’m repaired Stick usb 4 Gb!After installing ChromeOS,my stick has been memory unnalocated 3 Gb,but now is again 4 Gb!

  21. Awesome guide, exact same problem and got it fixed rather quickly. One problem thought was BootIt crashing while formating even with admin. Seems running it in comparability mode for XP did the trick.

  22. Thanks so much. I was afraid that I would have to buy another flash drive because I couldn’t find a way to get the memory back. You saved me ~$30. Thanks.

  23. Hi guy’s – Have a problem 😦 it didn’t work for me , i was trying a compatibility mode starting from 95 Win. and end with Vista… every time Run as Admin , it’s all the time crashing…. don’t know what to do !

    OS: Windows 7

    Flash: Kingston 8 GB

  24. BootIt crashed on me every time I tried to use it (and yes, I enabled compatibility mode and administrator privileges). I’m using Windows 7. However, I figured out how to fix this without this program: right click “computer” and click manage. Click “disk management”, then click your drive. Right click the affected partition (or whatever that empty space is) and click properties. Then go to the “tools” tab, and under “error checking” click “check now”. After it does this, reformat the drive, and you should have all of your storage back.

  25. Thank you so much! I’d tried installed some usb password protect program and couldn’t get back the allocated space. It occurred to me that if I’d messed up like that then surely others have. I googled it and there was your answer right there lol It worked just perfect, thanks!

  26. BootIT didn’t do the trock for me ( Windows Vista running as Administrator ), but I found a fantastic solution that cleaned my usb drive and left it as a raw partition I could then manage quite easily, see the steps below . . .

    run command promt
    type diskpart
    hit enter
    type list disk
    hit enter
    find out number for your fdrive
    type select disk X
    hit enter
    (X being the number for your fdrive)
    type clean
    hit enter
    type create partition primary
    hit enter

    that’s it

  27. Thank you So much!!!!

    I had a 8GB Sandisk when i installed Chrome OS, i only had 256 MB on it, used the program and followed instructions. Saved me alot of time and money.. Thanks!!

    • All of the above mentioned methods failed on me but this one worked! Just letting others know that even if the others fail, something can work. For me it was this!


  29. it didn’t solve my prob, the error “Could no write F:\BOOTLOG.PRV to destination.” prompt out and my flash drive still have unallocated space

  30. It didn’t work on my 16 gb flash drive but when I tried it on my 4gb flash drive it worked flawlessly. Maybe I will try it on our older xp computer in a little bit.

  31. Never mind dude, it crashed doing it but unknown to me it actually worked but didn’t say so. I reformatted it and it works great!! You just saved me more than 20$ it would have cost to buy new ones.



    if yo need more than disc repair ,,yo need old information from disc ,,so here is another way
    RECOVERmyFILES pro 4.9 ,,seach torrent ,,lmao

  33. ooooooooooo very nice its work ….. i thought i damaged my pendrive…. but your software restore my pendrive settings and unallocated space
    Thank you very much 😀

  34. Hey Folks,
    for those who have tried all of the above and failed to resolve the issue, here another tip.
    Use partition wizard, there is a free version for home users.
    You can download it at the below link.
    All I had to do was just to resize the existing partition and voila my usb stick was back to it’s normal capacity.

  35. dude just go to disk manage ment after right clicking in computer and if ur usb is shown as unallocated then simply create a new volume!!!
    so simple!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

    • Yea, but sometimes it breaks your USB and you >NeedAnything<, not even create a New Simple Volume out of my unallocated space on it

  36. Thanks, I tried to install Vanilla OS but thenI pressed cancel ’cause I decided I didn’t want it and then I had a bunch of crap partitions on my Lexar 8GB

  37. Hey man my 2gb usb is showing 2mb space only. i tried everything ran as admin and changed compatibility mode as well still it crashes while formatting. plz give a solution to this problem.

  38. Hi, I’ve tried everything you said lots of times.. but while it’s formatting, the program crashes..
    I’ve tried it on both Windows 7 & XP..
    The problem still persists and my 4GB pendrive is still showing me 3.89MB…
    Is there any other ways about how to fix this dude? Thnx

  39. Thanks dude… installed chromium os on my sandisk and that used 950mb on pendrive, after format rest of the space was unusable…. fixed it

  40. I had a major proportion of my ZEN style M100 mp3 memory as unallocated and Boot It did not work for me. However I have downloaded HP USB Disk Storage Format Tool – v2.1.8 which informed me that the Drive was content was protected. Leaving the HP tool open I returned to Ms Disk Manager and was surprised to find the disc showed as a full 7.47GB and format was available, so I formatted at FAT32 and I now have a full size drive again. A disconnect from the PC and restart and all is OK.

    This is recounted as best remembered but how it happened I do not understand because a negative result turned into a positive one.


  41. In Ubuntu,I used the delete partition feature under “disk utility” and created a new partition for FAT and its worked to recover my entire space again….

  42. Thank a lot for solution. It work!, I install esxi 4.0 then i could not for math by windows or dos. After i find this tools and try for math it amazing! so good.

  43. After a very interesting day of testing Chrome OS, I wanted to test a Linux based OS but my only pendrive was full even after formating. With this tool I manage to “format” it (for real this time) and recover all the pendrive space.

    Thanks a lot 🙂

  44. Thanx it worked perfectly on my Transcend 4GB pendrive. I got so worried when my pendrive shrunk to 1GB. I tried to boot Chrome OS from it. Thanx again.

  45. doesn’t work for me! but the stick works on ubuntu after creating a partition with gparted. but windows does not format, nor create a partition. the tool BootIt from Lexar doesn’t recognize it netiher.

    • Now I’ve been able to format it to fat32 with gparted and it works also on windows but when i try to format to ntfs, that i need for making a bootable windows usb, it says there’s write protection!

      • OK i got it! after formatting it and creating a fat32 partition with gparted on ubuntu, the Lexar tool finally recognizes the stick and now it fucking WORKS 🙂

  46. Ananth, thanks it worked. I got my 6GB back. thanks to you
    “This process can help u with out doing all above things:
    Step 1: Run -> CommandPrompt ->
    Step 2: Type diskpart ->Enter
    Step 3: Type list disk ->Enter
    Note: (Find out the allocated number of your disk)
    Step 4: Type select disk X ->Enter
    Note: (If X is the number for your drive)
    Step 5: Type clean ->Enter
    Note: (If you want to create partition in desired disk continue next step, otherwise ignore it.)
    Step 6: Type create partition primary ->Enter
    by Ananth”

  47. Pingback: Not able to use pen drive after cleaning it using command prompt

  48. Go to computer and left click Manage and open disk management and choose any thing local disk and left click shrink volume and click ok and background your choice making your local disk and left click new volume and next in each side and click ok your new local disk are ready and use

  49. my thumb drive letter does not shows under devices column. also diskpart cannot create a primary partition on this disk. but is there any solution?

  50. my thumb drive letter does not shows under devices column. also diskpart cannot create a primary partition on this disk. is there any solution?

  51. i have the same problem but i’ve been receiving a cyclic redundancy check error…. what will i do. i cannot partition my usb in the command prompt as well as in the computer management.

  52. please can someone help me, i have a hp 8gb flash drive, if i connect it to my pc, i get a massage that windows needs to format the drive before it can be used, but if i accept, it says, windows was unable to format the drive, i tried using command prompt to clean the drive, but i get a error massage saying “diskpart has encountered an error: data error , see the system event log for more information”. please i really need help, don’t have money to get a new flash, by the way, my disk management recognizes it as an unallocated disk space.

    thanks alot for i know u guys will help me out

  53. This worked for me, and better that it doesn’t requires any external tool. You should mention this technique in the post instead.

    Thank you!

    This process can help u with out doing all above things:
    Step 1: Run -> CommandPrompt ->
    Step 2: Type diskpart ->Enter
    Step 3: Type list disk ->Enter
    Note: (Find out the allocated number of your disk)
    Step 4: Type select disk X ->Enter
    Note: (If X is the number for your drive)
    Step 5: Type clean ->Enter
    Note: (If you want to create partition in desired disk continue next step, otherwise ignore it.)
    Step 6: Type create partition primary ->Enter

    • if i do this will it wipe out all my files ? I tried to get my mac formatted hardrive on a pc and i messed it up it now says unallocated disk space and i can’t get it on my pc or mac but i have files i do not want to loose !!! Help??? Thanks

  54. Pingback: Pny Flash Drive Repair Utility

  55. Pingback: Usb Flash Drive Space Problem

  56. Thanks, sandisk cruzer u 32gb unallocated space 24gb couldn’t find a solution, i actually thought i’d been ripped off until i found this blog! 🙂

  57. Thanks it helped me , i am trouble shooting 8gb pendrive , using diskpart inbuilt windows tool i could not able to solve Problem faced is disk number was not displaying

  58. hi there , I tried so many solutions even the diskpart thing but still giving me 4MB size , is there anything else I can try ????

  59. Hi Frnds…
    I am trying to format my pen drive but unable to do the format.
    It is showing the below errors.
    1. Windows was unable to complete the format.
    2. And also I had tried with command prompt but it is not working it showing the no disk selected.

    Friends do the needful to get my pen drive back , I have only one pen drive with me.

  60. Hey… I have a pendrive (16 GB) and one day after my friend used it, it does not show its space when i plug it into my i tried formatting it (using win 7 default program to format) and it shows format was unable to complete.also the capacity was shown as “unknown capacity”.then i tried diskpart .it showed Error and asked me to check the system log for more info.Is there any way that anyone could help me get my pendrive working normally again?..Thanks in advance : )

  61. This is the error i get using disk part

    DISKPART> list disk

    Disk ### Status Size Free Dyn Gpt
    ——– ————- ——- ——- — —
    Disk 0 Online 465 GB 7168 KB
    Disk 1 Online 14 GB 14 GB

    DISKPART> select disk 1

    Disk 1 is now the selected disk.

    DISKPART> format fs=fat32

    There is no volume selected.
    Please select a volume and try again.

    DISKPART> list volume

    Volume ### Ltr Label Fs Type Size Status Info
    ———- — ———– —– ———- ——- ——— ——–
    Volume 0 F DVD-ROM 0 B No Media
    Volume 1 E DVD-ROM 0 B No Media
    Volume 2 System Rese NTFS Partition 350 MB Healthy System
    Volume 3 C Windows NTFS Partition 49 GB Healthy Boot
    Volume 4 L Downlaods NTFS Partition 100 GB Healthy
    Volume 5 G Games NTFS Partition 146 GB Healthy
    Volume 6 K Linux NTFS Partition 28 GB Healthy
    Volume 7 M Media NTFS Partition 140 GB Healthy
    Volume 8 D Removable 0 B Unusable

    DISKPART> select volume 8

    Volume 8 is the selected volume.

    DISKPART> format fs=fat32

    0 percent completed

    DiskPart has encountered an error: The parameter is incorrect.
    See the System Event Log for more information.

    DISKPART> clean

    DiskPart has encountered an error: Incorrect function.
    See the System Event Log for more information.

    DISKPART> format fs=ntfs quick

    0 percent completed

    DiskPart has encountered an error: The parameter is incorrect.
    See the System Event Log for more information.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s