I've been noticing lately that the amount of disk space on my C drive was below 10 gigabytes.  This struck me as odd because I recently upgraded my 160GB hard drive to a 300GB hard drive and it wasn't like I'd suddenly started carrying around my entire DVD collection on my C: or anything.

This morning it was down to 7GB free.  I ran TreeSize Free to see what was going on.  I cleaned up about 10gigs of old junk and then I noticed that TreeSize was telling me that all my files totaled up to only 124GB.  What?!

Some googling around about Vista and missing disk space and I found this post about the Volume Shadow Copy Service (VSS).

I ran "vssadmin list shadowstorage" and found that VSS was using 142.712 gigs of storage.  ("Well, there's yur problem!" -A. Savage)

Then I ran "vssadmin resize shadowstorage /For=C: /On=C: /MaxSize=5GB" and VOILA!  I've got 185GB of free space now.

-Ben