Unix machine re-boots at random

This machine is my current server that will soon be replaced, but, would
still like to fix for a backup. PII 400MHz. My problem with this machine
started last Thursday with a "PANIC" error message. From my past experience
with this I replaced the 128 MB of memory and replaced it with two 256 MB
sticks. When I plugged the machine in there was nothing, no power. I got a
new power supply, and it started up. Thought everything was fine.

This machine has been running 24X7 since 1999 and has never had so much as a
hiccup. Now, it could run for 8 hours straight or as little as 30 min. It
just re-boots without any delay between boots (as if the reset button was
touched). Something may have gone wrong when I turned it off and let the
machine cool down for a day while getting the new memory.

Does anyone know where the most likely place for this problem is?

Mother Board?
Processor?
Raid Card?
Memory?
Power Supply? (I suppose I could have bought a brand new defective one)
Comtrol?

Thanks in advance for your help!

Frank




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