why is my computer not working...?

Check the power outlet cord plugged into, could be tripped circuit breaker/blown fuse.
Then check the power supply on the computer itself. If that checks out, make sure
cables and cards haven't worked loose, check RAM modules, hard drive and other
drive cables. If all of these check "OK", then the motherboard may be suspect,
possible capacitor blown/transistors fused, etc.

Hi

i have seen that with a loose agp card once. i suggest reseating all cards/ram, etc if its not the powercord or 100/240 switch on the ac supply or the surge supporessor.

You need to test your power supply and make sure the voltages are appropriate for each connector. If that checks out fine then you should examine the capacitors on the motherboard and look for bulging, discoloration, or oxidation. If no damaged capacitors are found remove memory and try to boot. If you are still not getting any sign of power remove all of your 4-pin molex connectors from associated drives/media/fans and try starting it with only the motherboard connected to the power supply.

Usual culprits for this problem are the following:

1. Power Supply
2. Motherboard
3. Memory/CPU/PCI cards

Also... Check to make sure you don't have a conductive material making direct contact with the motherboard AND the case. This can ground out the motherboard and cause the system to not boot. It can also damage all associated components of your system that are directly attached to the "grounded" motherboard. I've had this happen once before on a client's pc. Thankfully after removing a loose screw that had fallen beneath the motherboard the system booted again and everything was ok.

Good luck!