PC restarts at random [Resolved]

I've been having multiple problems with my Windows 98 development PC getting generally flaky so I replaced everything except the HDD.

Unfortunately it now cuts out and restarts at random every 3-15 minutes.

It looks like an overheating problem, but the new case is a big airy server case with 5 separate fans which I have set up to get a good through flow. I've also used a top of the range coolmaster heat sink and at the time of the last cutout the heatsink temperature was 17C while the BIOS reports a chip temperature of about 22C.

The installation of Windows 98 should have been pretty clean but just in case it was a reg/software problem I've tried the hardware with Windows 2000 and XP Pro and find the same problem.
:(

http://memtest86.com/ can check for bad memory.

Thanks - will try it

Yes that was it the new RAM that I bought from scan.co.uk was corrupted:(

(I put it in in a properly earthed antistatic environment)

Thank you very much JoshT!