[Rational Thought]

I have an old Dell Dimension which I put back into service after sitting for a couple of years. I decided to put 2 X 512mb’s of ram in instead of the pultry 256 I had been running. Guess what? Same symptoms that the OP had. No beeps at all...fans would power up for a couple of seconds, then go off, then come back on. In my situation, I swapped the Partiot PC3200 out with some PC4800 I had....and the system booted up. It surprised me too.

[Viking2002]

Yup - I'm a Dell tech, among other certs I have. Retry the old memory. It may have broken a contact just from sitting around, or it may also have built up a little corrosion on one of the DIMM contacts itself. The silver ones are notorious for that.