I think it is most likely a graphics card issue, but if you are overclocking anything return it to the default settings.
Boot the system into safe mode (push F5 during start up). Uninstall any video card drivers and reboot.
If the system starts up then that is the problem. Install the latest drivers from your graphic card homesite.
If it still doesn't work, boot back up into safe mode and, if you have created a restore point, one, restore your system to a previous state
If the worst happens, and throughout this you cannot even boot into safe mode, then I am afraid a reinstall may be your only choice.
Edited by uhaligani, 06 June 2007 - 04:54 AM.