Onboard video works,only if expansion plugged

Hello,
The deeper I dig, the more questions I have, my onboard video was not working, i purchased a new pci video card and it didnt work either, i hadnt got the post beep, no led activity and a blank monitor, i took a suggestion to disconnect everything, including power and hold the pwr button for 30sec before reconnecting, pwr cable, monitor, mouse, keybd, when i restarted the computer, it gave a post beep, but still blank screen on monitor, i detached and reattached the memory stick and still nothing, jus for the heck of it, i disconnected the cable from the video port I install and plugged it into the onboard video port and tadaa it worked. I didnt know if it worked cuz of what i did or what, wasnt sure if i would still need the new video card, so to test it, i uninstalled the video card (mind you that i never got a chance to install drivers yet) and plugged everything back up and was back at square one, i reinstalled the new video card, monitor didnt work on either ports, i disconnected everything and help pwr button for 30sec again, restarted computer, got my post beep, video was displayed on onboard video port but not expansion, so my question is, why is it that my onboard vid card only works when the new video card is attached to the pci slot and how can i fix this? I know that once i installed the video card, it should have disabled the onboard one, but in my case its vice versa. any advice?


Nat