Make sure it\'s a AGP card before doing anything here..
Disable the onboard graphics for starters. If the graphics are screwy on the boot screen, then your card could be screwed. Also check to see what your AGP settings are in your bios. If you have no idea, just use load defaults in bios and that should help. Just make sure onboard GFX is not on.
If it\'s just doing it only in windows, uninstall your old gfx drivers, with the onboard card enabled, (without the AGP in) Then reset your computer, disable the onboard card, Install the new one and install UPDATED drivers for the card.
If you have any other AGP cards laying around, (I doubt it) just test that card in the AGP slot to test the mobo, if it does the same thing then you\'re mobo could be screwed. Most common thing that makes graphics screwy while NOT in windows is hardware fails or faults. Disable anything in bios like “Fast Writes” or “Sideband addressing”.
If you have no idea how to get into bios, or what to alter in bios, remove your bios battery for about 10 minutes without the pc being plugged into the power. It looks like a flat battery on the motherboard.. It will reset your bios.
Resetting your bios will set defaults, but if you have the agp card in you must disable the onboard graphics.
Also check your Monitor plug pins. They may have been bent.