At first, my smart-aleck comeback was 'well learn how to shoot pool,' but seeing as you need a little help here, I'll add my two-cents worth and keep it technical and not related to bar games with long sticks.
This sounds like a hardware or buggy driver error. I'll assume everything on your system was working just fine, that no new hardware has been added, or that drivers have been updated, and that this blue screen just came out of the blue (no pun intended).
If that's the case, it sounds like memory to me. You can download an free ram checker and run a series of test on it, if it is memory related, this application will let you know. If that is not the case, and something had changed before the blue scree, you'll need to figure out what it was.
The easiest thing in that case, is to boot in safe-mode by pressing F8 at system boot time. Once in safe-mode you can disable the affected driver, uninstall the new software or whatever the change was. One last thing you can, either in safe-mode or normal operation mode is a system restore, that is roll the system snapshot back to a time before the blue screen happened.
It is determining what happened to cause the blue screen that can be most often the frustrating times. As I indicated, I believe to be a memory issue, and since most memory is installed in pairs (ie. you have 1GB, it will be installed in 512MB pairs), you can power down the system and pull each pair one at a time. If with one chunk in and the system doesn't blue screen, but does with other RAM chunk in, then you've found your bad RAM.