Using onboard and pci-e video card for dual monitors?

is it possible to use an on board video card and a pci-e video card together to extend my desktop? they both work fine by themselvs but i cant get them both to work together...what can i do??? THANKS





Comp: dell inspiron 545s

video card: ATI RADEON X600 Low Profile PCI-E Express Video Card

onboard video card:???|||No. Typically using an add-on video card causes the onboard to disable.