Plug the monitor into the card and reboot. Check the BIOS and make sure the integrated video is still disabled.
The reason there was no picture on the monitor when you moved the cable to the new card while the machine was already booted up is because you did not enable it and extend your desktop on to it. You do this by right clicking the desktop background and going to properties. It is in there some where. I don't remember what the tabs were called in XP.