I'm going to edit this thread a lot because I'm afraid the PC will crash while I type.
Sometimes it doesn't even boot, it never gets to the first screen. And when it does boot, it might crash within a few minutes.
It started a few days ago with just 1 crash while I was playing SC2. I thought it was because of overheating; I've had that problem before and I fixed it by dusting the whole PC. But right now I have crashes long before things start to heat up. I dusted my PC anyway and it made no difference.
It seems pretty random too: sometimes it won't boot, 2 minutes later it does.
I just ran WhoCrashed and it recognizes 2 recent crashes. Apparently "ntkrpamp.exe" is the criminal for these crashes. At the moment I cannot use Google to see what kind of program that is. I'll have to check that tomorrow, or if you want to check it for me that would be nice.
I have this feeling that it's a hardware problem, because most of the time it happens even before Windows starts.
Any idea what it can be? Any idea how I can find out (before bringing it to a store and pay)?? Thanks a lot.
Edit: recently I installed a USB headset of Creative. Maybe that has something to do with it?

I think that's the only thing that has changed on my PC the last few weeks.