I have a Compaq Presario 5204. When I turn it on, nothing happens. There is no fan noise, no sign of anything, as though it were unplugged. I think that it is the power supply, but I want to be sure that it is not something else, as a replacement power supply for this computer would cost $120.

take everything out cept for RAM CPU and VID, then try it. If still nothing, then yes, it prob your PSU. You can be amused by the simplest of things. The smartest people in the world, over-look the smallest objects. War does not determine who is right, only who is left.

Jeremy: $120 for a replacement Compaq power supply? That must be direct from Compaq. I suggest you do some google searches. There are other parts/model numbers on your computer/power supply. Perhaps the power supply is one of the model numbers listed here: http://www.affordablesurplus.com/compaq_presario_power_supply.asp These are only $34.99.

Actually, I was so annoyed by the $120 cost of those power supplies that I just opened up the power supply, blew all of the dust out (there were two inches caked on!) and took out and put back a fuse. After putting it back together, the power supply now works. However, there is something odd I heard online about power supplys. Can something called a "capacitior" kill you if your power supply is unplugged from your computer and the wall? If so, I took a big risk in fixing that thing. I didn't know anything about it when I fixed it.