Did you use a Dell replacement power supply?  This model uses a non-standard ATX supply and if you use a standard ATX one you risk blowing the motherboard and the PSU.  The power-on circuit is just a wiring through of the front panel ON button to two pins on the "ATX" connector of the power supply.  If look for the pin outs of the Dell connector (search this board or the Optiplex ones) you can find the two pins you need to short to turn the power supply on; this will allow you to verify whether the power supply turns on or not (i.e. whether the fans turn on).  But don't do the above or play with the power supply itself unless you know what you are doing....

Hi! Thanks for the response. Yes, I bought the supply from Dell. The order person told me it was the required model even though there was slight difference in the model number on the supply.

Thanks again,

Bob

Hi Bev!

Thanks very much for the information. I believe the voltage pin outs might help me track down what is going on with this machine. I need to replace it, but right now I need to get it running so I can retrieve the tax data that I have on the hard drives.

Thanks Again,

Bob