|You do not have to disable the onboard graphics in Vista, in fact, you shouldn't.|
You have to go into the BIOS & change some settings. It varies from system to system so here are some possibilities:
- disable onboard video
- change initial dispaly first to PCIE
- change shared memory to zero
Make sure your new card is fully seated in it's slot & if it requires an aux plug-in from the PSU, make sure it's connected. Connect the monitor to the new card & bootup. If the HP/Compaq splash screen doesn't display when you boot, there's probably a problem with the card.