Computer Keeps Crashing While Running SH3

[Subnuts]

I seem to be having the worst luck with SH3 these last couple days...

I'm running SH3 v 1.4 with GWX and no other mods. I can start a new mission or campaign or mission just fine for up to 20 minutes, and BAM, it happens. My computer just shuts completely down, and I'm staring at a "no signal" message on my monitor. I uninstalled SH3 and GWX and reinstalled both, making sure all traces of the original were removed from my PC. Same problem again. I'm not getting this problem with any other programs on my machine, so I'm assuming it just hates SH3. Anyone have any ideas of what might be going on here?

I swear, when I get a new computer, it's not going to have Vista installed. It's as gamer-friendly as a kick in the crotch.