I recently purchased a GeForce GT430 but the mobo will not recognise it. The MOBO is PCI-e and I have what i think is a suitable 400W PSU. I have changed the bios to look at PCI-E over mobo VGA and downloaded latest drivers.
How old is the motherboard? It may require changing the default video in BIOS if it is an older board. If you are going from integrated video to a discrete card for the first time, don't forget to move the video cable to the new card.