yay! Finally a really really technical problem
I repair computers for ppl and businesses so I see stuff like this all the time
If the blue screen stays for a readable amount of time, then it's most likely in the virus realm of problems. If it specifically says a memory sharing or permissions error occured and that screen came up to protect whatever, then that's baaaaad and we'll pretend it doesn't say that for now (but PM me if it does) If it only stays up for like a second or less then your comp shuts off, your graphics card or other hardware is fried. Since you said every time you start a 3D game, your comp shuts off there's about a 99.999% chance your card is damaged. If it's an AGP card, as in it's stuck in a different colored and sized slot on the top of your motherboard like this:
if it's one of those wonderful on the motherboard pieces of crap, you may be able to solve the problem by getting a PCI graphics card that will override the on the motherboard one. PCI cards go in any of those white slots in the picture above after busting out the metal thingy on the computer's case that's a placeholder.
I'd suggest replacing your current card with an Nvidia MX4000 card for about $40 at Walmart of newegg.com cuz it's cheap, AGP, and works pretty well running SRO. I think they make a PCI version of it too but AGP is faster if U got that slot. And don't worry, the hardest part is probably opening your case
other than that, just shut off the computer, take the old card out (it's the big card-like thingy on the inside that the monitor cable is attached to on the outside) and put the new one in. There might be a release lever like in the above picture but that's about it. Your computer will use a default driver for the new card until it finds a better one, which should come on a CD with the new card anyway. Then close up the case and tada
oh and vacuum it out while you're in there so your fans don't jam
