PC will not start up all of a sudden. I see the CPU fan running and the power supply tester I used showed it was all right. The boot post does not even initiate.

the problem is in your motherboard..this most cause unregulated flow of power from the source electric..but if the green led is off so its the processor.try to test it with a motherboard tester..or get another board that same spec with the you have,and transfer the processsor if it is working

This is either a bad power supply, bad motherboard, bad RAM, or bad CPU. You can find ATX power supply testers for around $15 to test the power supply. You can also swap RAM pretty cheap, so hope it's either of those, because if it's the motherboard or CPU it's going to cost a lot more.

Change the setting in the BIOS menu. reboot your computer.. when you see the dell logo.. press F1 (or F2 if F1 doesn't work) button until you see the BIOS screen. Check for fan options and change it

check to see that it is not overheating. If cpu fan is not blowing (could be frozen up) or if the fan in the power supply is clogged with dust, the computer may be overheating and refusing to some on. If it is dust, arrange to blow it out completely. take off cover and try to start the machine, the fan should turn on the CPU.

sounds to me like your mainboard is bad, i bet if you closely inspect the capacitors around the cpu one or more is bulged out or leaking

Which fan are you referring to? As far as I know the fan in the power supply runs at the same speed at all times. So if that is the fan you are hearing it may indicate that the power supply is failing. The power supply may be over heating and shutting down. I would try a different power supply if you can get your hands on one.

do you have an extra power supply?

if it has...isolate your power suply...so that you will know that your power supply work properly..

thanks........

Remove all parts from the motherboard PCI slots, AGP slots and such, including all drives and RAM memory sticks.

If you still cannot get to a boot screen, have the power supply checked out or get a power supply tester ($25 at most) and test it yourself. If it checks out OK, then try swapping your CPU out into a similar computer to test it.

If the CPU works, disconnect everything from your motherboard other than the power, this includes all RAM (memory) sticks any hard drives floppy cd, etc.

Boot the PC and see if you at least get to the BIOS boot screens (White type on a black bacground) If you do, then put them back one at a time, rebooting each time. This will allow you to narrow the problem down to the part causing the problem.

Replace the problem part.

That being said, it will most likely be the power supply in your system causing the problem. They can be replaced fairly easily.

REINSTALL WINDOWS

plz try with new power supply