Windows 7 Bluescreen

Apparently I have a virus or whatever in my Windows 7. I can’t be online more that thirty minutes before my computer crashes and I get the Blue-screen warning. “Windows has encountered a problem and must shut down”. So then I have to shut down and or reboot. When I shut down the logging off sound is like a high pitched sound of teeth grinding together. I have tried Norton Deep Scrub without success. Norton can’t find any infected files. So now I am using Avast Pro, also without any success. I am using the Firefox browser. Does anybody else have this problem or am I the only one?

Follow this guide, and attach the logs from malwarebytes quick scan / OTL / aswMBR
http://forum.avast.com/index.php?topic=53253.0