46 GB of hard-drive is <Unknown>. HELP!

[Tom]

Running Vista on Thinkpad T60..

Problem: 43,9%* of the 105 GB hard drive** is taken up by <Unknown> files.
- How can I reclaim the desperately needed space on my drive?

Disk has been repeatedly defragged and thoroughly cleaned (both with Vista
and CCleaner). System restore and automatic backup is disabled (from day 1).
C:\System Volume Information\ contains only 24,0 KB.

*WinDirStat analysis
**Toshiba MK1234GSX

 

[BurrWalnut]

WinDirStat shows where disk space is being used including a graphical
display. Just let the mouse pointer hover over the coloured areas to identify
different file types, here http://windirstat.info/

Ways to reclaim space:
-If you don't use Hibernation you can save yourself up to a gigabyte of hard
drive space by turning it off. In a Run window, type powercfg.exe -h off
(note the two spaces) and press Enter. To turn it back on type powercfg.exe
-h on and press Enter.
-Reduce the amount of space used by system restore. To reduce the amount of
space, open an elevated command prompt by clicking the Windows Orb (Start) >
All Programs > Accessories and right-click Command Prompt, then ‘Run as
Administrator’. To display the current parameters type (or copy and paste)
“vssadmin list shadowstorage†(not the quotes but the spaces) and press
Enter. To reduce (or increase) the disk space allocated, type (or copy and
paste) “vssadmin resize shadowstorage /on=c: /for=c: /maxsize=3GB†(not the
quotes but the spaces) and press Enter. This example assumes changing the
space on drive C to 3GB. You may find that all the restore points have been
removed after resizing so make sure the computer is behaving itself before
reducing the space allocation. Also, make a manual restore point immediately
after resizing.
-Reduce the space used by the Recycle Bin. Right-click the Bin > Properties