check the memory.. to make sure you diddn't fry it first off (pull out one stick and try one at a time in the first Ram slot) (memory is the most volitile and easy to damage incoherintly computer part In my opinion)
next try the vid card in another comp to make sure that's fine (don't let the comp boot to windows though or it will screw up the windows configuration a bit) just mash the del key and go to bios and see if it displays fine...
Next thing would prob be to reset the cmos if none of the above showed anything :/