More info would be good, However, things to check:
Reseat ram
Pull cpu and reseat
Reseat vid card
Check to make sure vid card has power dongle hooked to it, if need be
Check to make sure board isn't grounding to chassis
Make sure board is not grounding out at I/O shield
Pull and reseat power to board.
All of these thing are to be done with power off, and power cord removed from power supply.
Advise as to progress to get more help
EDIT: Try ram in different slot/slots to determine if that is the problem after trying all of the above first.