I Assume, that Windows doesn't start? Please go into your BIOS (mostly by holding ESC, DEL or one of the F-Keys (F1, F2...) directly after pressing the power button until you get the message "loading BIOS" etc.
There you have to search the option "Init Display First". What does it say there as a value?
And: What graphic board do you use (How is it connected? AGP ? PCI ?)