Dell computer, no warranty. Was brought to me by a co-worker. It is almost 6 mos. old. She turned it on and nothing happened. Dell said it was the PSU. She baught a new PSU. I put it in and... NOTHING. No activity at all. No beeeps, no fans. There is a light on the MB that is on when the PSU is plugged into the MB, but that is all. I have disconnected everything and reconnected in various sequences, but still nothing. Any thoughts?

more than likly a proprietary PSU. test the PSU on its own. take out of case and jumper pin 14 to any black one. here http://www.hardwarebook.net/connector/power/atxpower.html plug into wall and turn on. if fan comes inside PSU, its prolly ok. and why does this not have a warranty. I though systems had a 1 yr from manufacturer.

She said she did not purchase a warranty so it was only covered for 90 days. When you say jumper, excatly what do you mean? Is this something I can do with a paper clip?

Like squirrel said, Dell has used power supply/motherboard combinations that are proprietary. In other words, you might not be able to replace either one with a generic power supply or motherboard. In fact, if they are proprietary, you could damage the motherboard by installing a generic power supply.

You can find some info on the Dell proprietary power supply here: http://www.quepublishing.com/articles/article.asp?p=339053&rl=1

I have a Dell replacement power supply that I'm using now. Still nothing.

If you have replaced the psu and the system still just sits there, then the next logical step is to test the front panel button. Look on the motherboard for the connection header. Find the two pins the front button plugs to and jumper them with a small screw driver or something metal. Be careful you jump out the right two. If it fires up then it's the button if it does't then the circuit on the motherboard that latches the psu on has failed. I may be crazy, but I'm not stupid...