He has a nice machine, the ATI 9500 XT video card, easily enough hard space for BZ2 with a 120 GB hard drive and a really fast processor. He also checks constantly for viruses. It is purely BZ2.
It is also a clean reinstall of BZ2.
Overclocked? BZ2 puts a lot of strain on the CPU regardless of the video card.
I've got a similar problem with my radeon 9000 chipset in my laptop...if i get in and out of bz 3 or 4 times, i get a BSOD.
Of course, changing the screen resolution the same number of times does the same thing. I have the latest video driver (over a year old...Dell doesn't give a rats ass about complaints on their message board...they're on to selling new stuff now.)
Like ZA said overclocking too much will cause problems. BZ2 will give me a BSOD restart if my comp is OCed to high.
Heat caused from OC could be one reason, though driver conflicts also can cause blue screens.
No overclocking for me and my computer BSOD's when I try to do anything else besides BZ2, it is one of the few games that actually runs perfectly on my computer.