Guaranteed crash/hang while Gaming! Help!

Hey all, first time poster here. I'll 'try' to as brief as possible.

So I recently built a new computer (first custom build), with Windows 7 64bit and the rest of the parts listed in my specs. Runs great, except when I'm gaming. Problem is that I can hardly go a half-hour without the game crashing, getting a BSOD, or more than likely, just hanging. Also happens when I use Firefox.

Sometimes it'll CTD, though that seems kinda rare, usually it'll just hang and I'll hafta reboot. So naturally I assumed my problems were with Windows 7. So I re-installed XP earlier today, and lo and behold, I'm having the same problems.

These crashes started not long after I had it all put together (except for the vid card, which I just put in a couple days ago.) So, new vid card didn't fix it. My drivers are up to date, and I even tried some older ones. Everything is new, I keep it clean (regular virus/malware scanes, CCleaner, etc).

I don't think it's the drivers, as they're the latest from nVidia, I'm pretty sure it's not a heat issue (my case has 5 fans, and liquidcooled CPU that hardly every gets above 35c). It's never crashed on start-up, or anything like that. Only when I'm gaming, or using FireFox. Also, doesn't matter what kinda of game, single-player or online. They all go down pretty much the same way.

At wit's end here, don't know enough about troubleshooting to fix this myself. ANY help would be appreciated =P

I've attached my one and only .dmp file since re-installing XP, btw. I realize this is the 'sevenforums', but I don't know where else to go >.<

Wow, that's about the last part I would have suspected. Here I was thinking it could be faulty RAM, or my sound card was too close to vid card, or something...

Anyway, thanks a lot man. At least this gives me a place to start =P

Appreciate it.