No beeps? Nothing? If so...
1st pull all non-essential cards out of the motherboard. Leave only the video card, master HD, CD, and floppy. Make sure the ram chips and video card are seated correctly. If you have more than 1 ram stick, take all but one out. Switch them out 1 by 1 and see if that fixes the problem. Double check your power connections. Make sure they aren't 1 pin off, and also re-check that the jumper settings are correct for the processor.
If it still fails to do anything, re-set the bios (usually a jumper). If it still wont crank, change the CMOS battery. If that fails, try a different power supply. If you still have no luck getting it to fire up, chances are that;
A.) The CPU is dead
B.) The motherboard is dead
c.) All of the above
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~Hitachi
Whiskey Tango Foxtrot, interrogative, over.
Savage Vision