I have an WinXP with a P4 processor and when I turn the computer on it looks and sounds as everything is normal but I get no video.
Things I have tried:
Removing all PCI devices
Removed power from cd-rom, dvd-rom
Tried a different video card
Removing all peripherals ie. mouse, keyboar
* I tried another power supply but I don't think it was compatible with the computer in question.