Motherboard problem?

Hey guys
Last week, my comp shut crashed out overnight. When i found it, the monitor was still accepting signal and the wireless mouse receiver was still accepting signal as well. i hit the reset button and the fans powered up, hds chirped, then nothing- no beeps at all. no signal to monitor or mouse/keyboard. i read up a few posts here at work and tried the 'insert key' trick, and it powered up. the only peculiarity from it was that it read DDR: 266.
I have 3 sticks of DDR 400 (512/) and i just figured it was something with the bios and didn't fret.
Yesterday, it happened again, but couldn't get the insert key to go. i opened the case and reset the CMOS and powered up. Got the beep and the initial read of memory (157600ish) and then the DDR post- this time at 200. at that time, the system hangs. i can restart it and it does the same thing continuously. If i go into bios and change anything, it crashes again on reboot and i have to reset the CMOS again. i tried removing all but one stick of DDR and no luck either, the memory reading is accurate at start up.

My system config:

abit AT7 Max2 motherboard
amd 2700+ cpu
antec 430W true power psu
ati 9800 AIW pro
4 HDs - 1 raid array (OS)
3 sticks of 512 DDR PC3200

the middle fan on the motherboard doesn't run at startup and i figure this could be part of the problem.
Thank you for reading my long post, and here are the questions.

how can i be sure it is the motherboard vs the CPU?
i have my OS on a raid array (striping)- if i purchase a new motherboard with SATA, or a mobo and a pc SATA card, will that raid array still function?

thanks guys
dez

 

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