try to take out the bios battery,all power conectors and wait for 10 minutes. remove any unnecesary hardware, check the video card if is well inserted, then reconect all power conectors, bios battery and boot, i you secceed, then update your video card drivers maybe any file is corrupted. before you update the drivers, go to control panel, unistall your video card, (dont restart)
go to the folder where the drivers are, delete it adn then reistall the new drivers.
hope you solve your problem