|You didn't tell us which card? And you should NOT have installed any drivers until the card is recognized!|
Remove the video card from the Dell & connect the monitor to the onboard. Boot into Windows & uninstall the new drivers, plus the drivers for the onboard. If it tells you to reboot, do NOT do it. Then go to Device Manager & uninstall the graphics adapter (if it's stll listed). Shut down, install the video card, connect the monitor cable to the card. Boot the system & immediately enter the BIOS. Disable the onboard video, change the shared RAM to none, set the Initial Display to PCIE, save the settings & exit. If all goes well, you will get into Windows on the reboot, THEN you can install the new drivers.