Pci dual head vga/dvi video card hooked to 2 lcd displays shows only black screens?

trouble shooting steps: Im working with an XP machine, the card is supposed to be compatible with this OS.I installed a new 450 watt power supply.I uninstalled the onboard video drivers,disabled the onboard chipset in device manager; installed new drivers with cd and tried to open nVidia desktop manager but it wont open in control panel and isnt showing in start menu.when I connect the monitors to the dual head card both screens just show black, no desktop or even dos screens. Please any suggestions are welcome. I need help.|||Remove the nVidia Card, restart the PC, go into BIOS and rest to factory default, turn off, start PC up and see if the display come on with onboard video, if yes, shut down, plug in nVidia Card and start up, dont do anything with the onboard video settings.