Why does using 2 memory sticks cause my computer to crash?

"4Gb ram.
memory tests are OKAY.

Since you're running a 64bit OS, it's probably a buggy device driver.

If they ported the code form a 32 bit driver and left some 32bit assumptions in, then it will crash, particularly when playing games which are graphics ,sound and i/o intensive.

Look for newer drivers for your devices. Try getting only MS drivers. Try substituting other drivers one by one.
Sound would be my first guess.
then video
then network ?
then keyboard, other usb things etc."

"Here are some things I can think of is if you bought Dual Channel RAM with a motherboard that doesn't support dual channel. Every kit of multiple ram sticks I have seen have been dual channel kits however I can't guarantee this as I don't believe there are any hardware differences in the RAM itself, but in the motherboard.

On another note, how many slots do you have for RAM? If you have more than two (most modern computers do) I'd try putting at least one of them in a different slot. My motherboard can be picky about those things where if I don't put things in the right slots it doesn't like it. While this is probably a sign of a defect I don't have problems otherwise. Other than that I'm stumped."

"running win xp? 4gb is max ... may not be handling it well.

http://msdn.microsoft.com/en-us/library/aa366778(VS.85).aspx

it looks like you have tried everything else i would think of.

motherboard just may not be able to handle it. not sure."