There is malware that does this. Try an online scan such as http://www.ewido.net/en/onlinescan/
This first started after I used system restore to when I unistall kaspersky 7.0.
I don't know how to better describe the problem but when I delete some files the computer will show some free space but the number will keep going down to 0 bytes. I've deleted like 3 GB of files already so there's definitely something wrong.
Also in the windows task manager "csrss.exe" and "avp.exe"(kaspersky) takes up all of the remaining CPU.
I thought the problem might be kaspersky not being uninstalled properly because it kept showing errors of not being able to start up. I tried to uninstall it again but can't because there isn't any free space.
that's about all i've managed to do. please help. THX!

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic