It kinda sounds like a software issue to me.
First off, go into BIOS to check your temps and post them here.
Provided that temps are ok, you might want to try booting into safe mode. To get into safe mode, hit F8 a few times when your computer is booting up.
Intel E6750...........PSN: ELBATROP
XFX nForce 650i Ultra
Patriot PC2-6400 8GB (4x2GB)
36GB WD Raptor
Samsung SyncMaster 931c
Samsung SyncMaster 750s
Windows 7 Home Premium 64