Memory beeping error

I had a computer that kept restarting like a loop in windows 2000 professional after the white windows page. I cleaned the inside of the computer (It was very very dirty). Now when I start it up I get 1 lond and 3 short beeps which indicates a memory error. I reseated the dimm and sill got the error. I replaced it whith a known good dimm and still got the beep. I put the old dimm into a working computer and it booted fine. Do you thing the problem is the slots on the motherboard?