Since it is not beeping and not turning on the monitor, then it is not POSTing. Try clearing the CMOS. The other thing to check would be to reseat the RAM, or boot with one stick at a time. If that does not work, try installing a different card - you said you could try your's so give it a shot.
Also, what power supply is he using? If it is an old, no-name brand, or poor platform it may not be supplying enough power now to boot. On a related note, a lightning bolt took out my own Corsair HX750 and pretty much showed the same symptoms you are experiencing. It's possible that a power surge could have done the same to an older unit.
If after all that and it still does not POST, I would look at the motherboard, but only as the last resort.