I was just playing my first game of Crusader, messing around, learning the ropes and such. All of a sudden I get a blue screen that says something about a "pool" error (sorry I can't remember the whole thing, it happened so fast) and my PC restarts. Has anyone heard of this occurring? Can a game even cause a blue screen or is my really nice gaming PC dying :0 ???!!!

Of course a game can cause a blue screen. Any application can cause a blue screen.
Unless you're having repeated trouble with blue screens, I wouldn't worry about the PC.

I agree - unless this happens a few times then you should not have any fears. Though I would say a good policy is to always restart a computer after installing a game - infact I find with Vista its better to completly shutdown and start up with games that do require a restart.