Computer randomly restarts, or gives BSOD. PLEASE HELP!!

[Atomic Rooster]

I have NOT run a memory benchmark test, yet.
I HAVE inserted one memory stick at a time.

Run this: Memtest86+

 

[unbwogable]

So I swapped out my motherboard, and it's been running like a dream for several hours continuously.

Also, as a matter of trivia, my firefox stopped crashing randomly, and I was able to open several ZIP files that were supposedly corrupt (damn CRC errors!) on this new system, WITHOUT re-downloading them. Seems that old board was perhaps a lemon?