Did you install yet that video card in your System!!!!
Did you disable the Integrated Intel 82845G/GL/GE/PE/GV Graphics Controller) in Your Dell system !!!!
You should be able to disable the card in the computer's BIOS (it's integrated graphics, so it should be able to be turned off in the BIOS)
Keep in mind that Every BIOS is different on how to disable the onboard.
Some have an enable/disable setting, some have a shared
memory setting that needs to be set to zero (or none), some
auto-disable when a card is detected. You're gonna have to
poke around the BIOS & see what you can find. Other than that,
make sure to uninstall the onboard graphics drivers & if
necessary, go to Device Manager, find the onboard listing
under Display Adapter, right click on it, then click disable.
cheers..