Well it wasn't the RAM or that file that Avast found. The machine is doing the same thing. I am wondering if it is overheating...

Thats the other thought i had. How many Intake and exhaust fans do you have? and is the heatsink working properly
Dont run Avast in safemode, load up windows when it comes to the loading screen hold the shift key untill windows is fully loaded. then run the scan.

I would try restoring to an earlier restore point see if windows update has downloaded one of microsofts self destruct programs, they really do want us to buy windows7 dont they.