From what I've read, this has been a common problem. Let me tell you everything I've done so far to fix this problem. I apologize if my computer lingo is less than stellar. I'm learning as I go:
Unaccounted for, disappearing hard drive space on Windows Vista. Ran the vssadmin list shadowstorage command, changed how much shadow files can be stored, and still nothing. I have about 2GB of programs installed, 40GB of media, documents, and pictures total, no viruses, have run the disk defrag, disk cleanup, and emptied recycle. I still show only 37GB of 286GB free. My WD External hard drive says that the bulk of my memory is taken up by "system files," but I can't find files to delete.
As I said, I have malware protection, have done complete scans, and no viruses or infected files are found. I changed my shadow storage to 15GB, but my hard drive space didn't improve one bit. I'm not in a position to afford a professional to diagnose and fix the problem, so I'm open to any and all suggestions.