every day, the available space on my HD is shrinking with seemingly no explanation. available space went from 1.3 gigs yesterday to 800 mb today. this has been happening slowly for a week or two.

however, when I select all the folders in C:, it only adds up to about 6 gigs. I KNOW I don't have 32 gigs of stuff on here. there were more than 10 gigs free last month.

I tried unchecking the "hide hidden folders" option, thinking someone in my family might have a massive porn stash or something, but no, just the standard system files showed up.

I then did a search on "files modified in the last day" and even that seemed to be in order.

as an experiment, I turned off my modem and just let the computer sit for a few minutes. I lost 3mb in 5 minutes.

now I'm relatively certain it's a virus, but I'm pretty careful about what I download, and I can't remember downloading anything remotely suspicious at all recently. I don't even have Kazaa or anything like that installed. the closest is an FTP program (smartFTP), but even with that, I only download music or an occasional movie.

does anyone know what the problem could be?

sys info-
compaq presario 5000T
windows ME (I know, I know. family computer)
376mb RAM