Really thanks for your reply!!
Anyway, I've already formatted the PC, and the first thing I did was to disable the Windows Update of Device Manager, then I installed the BIOS and drivers downloaded from my PC's manufacturer's site. Guess what, it totally worked! I've been monitoring my PC for about a day, and fortunately BSOD never appeared!
I guess Win7's built-in Device Manager Auto Update is playing around. Is Microsoft aware of this issue?
Dude, thanks for everything!