windows does this when a driver does something its not supposed to do, as Raffaz said, there should be a code, we need this to see what driver is causing ur pc to blue screen.
Has the problem just started, or has it always been like that? If its just started then what were ya doing before it happened? Have ya installed any new drivers?
The problem comes from windows making improper memory dumps and is thus causing a memory corruption. The problem could be related to your memory modules. One or more might have stopped working properly (due to age or whatever).
Run memtest to be sure that there are no errors....http://www.memtest86.com/