I have a 40 GB USB hard drive formatted with NTFS on a PC running Windows XP Pro, SP3. I am trying to free as much space as possible. Windows Explorer tells me that I have about 200 MB of files on the drive (showing hidden and system files). When I show drive properties however it shows 73% free, around 10 GB used.

I ran CHKDSK and it found all kinds of problems.

Now running defrag and it is behaving as if there were 10 GB of files, but I can't access them anywhere.

How to find and remove this extra 10GB?

  • What OS is this for?
    – squillman
    May 17, 2009 at 17:36
  • Windows XP, added clarification to title
    – jacobsee
    May 17, 2009 at 22:11

4 Answers 4


Format? That's pretty much the smoothest way of cleaning out a filesystem.. replacing it. :D

If you are storing large files selecting a larger allocation unit will reduce overheads.

I went from about 300MB in the MFT to less than 10MB after formating with a 64K allocation unit and copying back the data. This was on a 250GB NTFS volume.

I'd also look at system restore. Try running WinDirStat as SYSTEM using PsExec and see if there are large files under System Volume Information named Restore{GUID}.

To delete all but the most recent shadow copy for every volume on your system, go to Disk Cleanup, select "Clean up System files", then use the 2nd button on the "More Options" tab.

To clear just one volume disable and then re-enable shadow copies for the volume from the "System Protection" tab of System Properties.

(If you're interested in the size of your MFT, look at the output of defrag /a)

  • that is a good point, cleaning out old system restore files can be a HUGE help in this area. May 18, 2009 at 5:30
  • Great suggestion -- ran Sequoia View as SYSTEM and it immediately showed me that I had about 3.7 GB of restore files. Disk cleanup was not able to remove them (why do I have restore files saved on my removable USB drive anyways??). Now trying to figure out how to delete as SYSTEM...
    – jacobsee
    May 26, 2009 at 14:44
  • I'll probably end up reformatting as per your other suggestions rather than mess with this any further...
    – jacobsee
    May 26, 2009 at 14:46
  • 1
    Disabled system restore for this drive only and that reduced the reported used size a bit. Then used psexec -s cmd to get a system shell and deleted the restore files. I'm down to 1.6 GB used. Disk defrag / analyze / view report tells me the MFT is 1.45 GB, so I'm going to try your other suggestion of just reformatting to clear that.
    – jacobsee
    May 26, 2009 at 15:17
  • after formatting and copying back the files, MFT is down to 160 KB, quite an improvement!
    – jacobsee
    May 26, 2009 at 16:40

There is a slight chance the missing space is in NTFS alternate data Streams - use the sysinternals streams utility to find out.

Alternate data streams allows files to be associated with more than one data stream. For example, a file such as text.txt can have an ADS with the name of text.txt:secret (of form filename:streamname) that can only be accessed by knowing the ADS name or by specialized directory browsing programs. Alternate streams are not detectable in the original file's size...

  • streams -s No files with streams found. Nice idea though!
    – jacobsee
    May 26, 2009 at 14:01
  • I wrote "slight chance" - sorry.
    – gimel
    May 26, 2009 at 16:07

Two points -

1) I have often seen on client (and my own) computers that when free space gets very low (less than 1%) when files are deleted, they do not free up the appropriate amount of space (delete a 1 gig file, only get 500 MB back).

2) I have never found a way to recover ALL of this space, but I have found a way to recover some, which I will outline below:

Steps to clear out the page file area -

1) Right click on "My Computer" and select properties

2) Click the advanced tab

3) click "settings" under "performance"

4) Click the advanced tab again

5) Under virtual memory, click "change"

6) Set the page file to 0 MB, then "okay" out of all the screens and restart the computere

7) Reset the page file to the appropriate size

That should help clear out some of the missing space.


Running TreeSize Free as LSA helped me, look at this, og how to run as LSA http://www.tech-recipes.com/rx/1288/how-to-run-applications-in-the-local-system-account-lsa/

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