BSOD = Blue Screen of Death
When Win XP is in the middle of scheduling an execution thread, it puts the processor at an interrup request level, or IRQL.....this blocks other software from iterrupting the processor until the process is complete..........this means that even DRIVERS cannot interrupt the current process (physical memory) while the IRQL is in play.........if something breaks the rule, then you get the BSOD.......what you have to do is find out what driver is breaking the rule.....
Does this only happen when you are playing graphically intensive games? If so, definitely start with the video driver. Otherwise, I would start Windows in SAFE mode, uninstall all of the "usual" drivers, and then resinstall fresh drivers, especially with your video card, sound card, USP controller....things like this.
This worked for me when I had that same error.
Did this just start happening?
Try taking out one of your sticks of RAM, playing for a while, and then replace it.
I would set everything back to default settings one click at a time until the problem is resolved. If not, you may consider backing up your system and doing a fresh intall (or repair) of windows XP.