try this link - http://forumz.tomshardware.com/softw...pict10993.html

I used to get this on my machine and it was heat related, it just decided to reboot on me whenver it felt like giving up. The intervals got progressively shorter between crashes. I moved the PC forward about a foot to get better airflow round the back, fitted a PCI exhaust card and its been fine since.

Try removing any recent hardware as well. If this doesn't fix, the easiest thing would be to back up all your data (docs, mp3's etc) and then rebuild the PC from scratch.

Cheers

Matt