I added a CD burner and a Linksys WIFI PCI card to a computer to give to someone to leech internet off their neighbor and I had to pull the main ATX plug off and move the HD's around (there were 2) to get all the IDE cables to plug in properly and after I put it all back together, I went to turn it on and got nothing. I forgot to plug that ATX plug back in. Took me about 5 minutes of thinking I fried something to figure it out.

Processors in correct and the ZIF lever is down. The 4 prong plug is attached next to the processor? Memory if full seated and in the correct slots? Should at least boot and make some noises.