Asus P4P800 + 2x512 Corsair XMS + 2 Other sticks == Problem?

[Slushie31]

I've had a P4P800 for a number of years now, with 2 sticks of memory on it: a 256MB and a 512MB stick, both PC2700, and obviously not matched. This morning I purchased a 2x512MB PC3200 Corsair XMS dual channel kit. The salesperson at the store told me that it should work fine with my existing set up.

 

Upon installing the new RAM, everything appeared to be working fine. Both the BIOS and Windows recognized that I now have 1792MB of RAM installed. However, within about 30 minutes of booting up, my computer crashed. This pattern followed in successive reboots (though some times it BSODed instead).

 

I called ASUS and was told that the four sticks should be operating in single channel mode because they are not matched in the channels (one channel has the matched Corsairs, and the other has the 512 and the 256). I confirmed this using Everest, a hardware profiler from http://www.lavalys.com/ (listed Memory Type, I believe it was called, as Dual, but Active Type as Single).

 

I have run memtest86, which stopped at 70% (the beginning of test 7), and wouldn't resume or respond to keyboard input. At the time, there were no errors found. For some reason though (I've never used memtest before and don't know how to set it up and if that's even necessary), it listed the FSB speed as 133MHz, when I know that it's 800. There were probably other discrepancies too, but I didn't catch them. (Memtest reported the memory as being in single channel mode too, for what it's worth). Memtest also sounded a number of 5-beep sequences from the PC speaker throughout testing (I'm not sure what those mean, if anything).

 

Does anyone have any suggestions for me? I'd really like to regain stability on my computer.