BSOD caused by RAM issues

Here’s the deal with my situation.

I'm running 2x2GB of RAM, where the first stick is a Crucial 667 MHz and the second one is a Kingston 800 MHz. Ever since I slapped that second stick in, my whole system just freezes up and dies every couple of days, throwing a Blue Screen of Death and an error message at me. This only happens while I'm gaming, and before I added this extra RAM, the game ran perfectly fine for over a year. To be clear, the RAM itself is fine. I've already done the defrag and cleared the registry, plus I used CCleaner and disk cleanup, and there isn't a single virus on this machine.

I should mention that about two years ago, I also picked up some 800 MHz RAM because I couldn't find any more of that Crucial 667 MHz stuff, and I had the exact same issue, just more frequently. I ended up selling them because I figured they weren't compatible back then.

The motherboard I'm using is this: http://www.asus.com/products/pro...px?pid=2695#ov it supports DDR2 up to 1066 MHz, has 4 slots, and goes up to 16GB total, so you can't blame the board.

I have no clue what the BIOS settings for the RAM should actually look like. I just tried something a moment ago where I pulled the CMOS battery out of the motherboard, waited five minutes, put it back in, and fired up the PC. The date in Windows defaulted back to 1/1/2008. It doesn't show the startup messages anymore, but when it lists the CPU GHz and the RAM, it shows 667 MHz instead of 533 MHz, though it says 64-bit now instead of 128-bit if I remember correctly. Also, the processor is sitting at 2.2 GHz per core instead of the 2.7 it was at, and at 2.9 it would just crash. Basically, I just reset the BIOS.

The RAM is running in dual channel. Here are some fresh CPU-Z screenshots:

http://www.zaslike.com/files/8oy3dat2qwpn4rp61nr.jpg

http://www.zaslike.com/files/91gh0h15n7ual4eqcktt.jpg

http://www.zaslike.com/files/505qsa2w97twoeezhq7.jpg

http://www.zaslike.com/files/r30rwklzpu8q9ryh2lk3.jpg

Usually, ASUS motherboards aren't super picky about MHz differences or which manufacturer you go with. But, if you really want to avoid any headaches, I’d suggest selling that Crucial 667 MHz stick and just picking up another Kingston 800 MHz one. That way, you'll have a matched set of 2x2 GB. Right now, your memory is stuck running at 667 MHz because the BIOS is automatically downclocking that second 800 MHz stick to match the slower one. If you had two 800 MHz sticks, they'd actually run at that speed. As for that 1066 MHz stuff, the manual basically says, "Whether 1066 MHz memory speed is supported depends on the CPU being used."

It’s pretty much impossible to find a single 2GB stick of Apple MacBook RAM like the one I've got, especially since all I see on eBay are these sets of two 1GB Apple MacBook sticks and nothing else.

There are just these two listings for those dual 1GB kits

and

technically that would hit 4GB, but since both slots are already taken, I have no clue if that would even function correctly...

I don't see any other way to handle this unless someone actually tracks down a single 2GB module identical to mine.