suspicious ram

my computer was going nuts about a month ago. turns out taking out the second stick of ram fixed it. so i put the working one in another computer and took both out of that one. and back into mine. so now i still had 2 sticks of ram, but from a different computer. now i was getting another problem. surprise it was the second stick of ram again. is it possible that my mobo is frying ram or something? i dont think the second one was in the same slot in both instances though, because the second set have a case and didnt fit right beside eachother.

That's entirely possible, but something to check before you replace the motherboard.
Replace the *power supply* with a *new* 500 Watt (or more) unit.
You can pick them up for $20-$40, and the more power you can cleanly feed the system, the longer it'll last.
If the PSU is feeding dodgy power to the system, it can show up as RAM errors, HD errors, video glitching, etc.
Try a new PSU first - if that fails to fix the issue, go ahead and buy a new Mobo+CPU combo, and keep using the new PSU.

Hope that helps. =)