Disable any onboard graphics in the bios, if it is not. Then try both of your cards together.
Also in bios, assuming your Radeon is PCI-E, make sure PCI-E is selected as the default first display. If your Radeon card is AGP, make default first display AGP. Not onboard or PCI.
If that doesn't work, you can try moving the single output cheaper card to a different PCI slot. Switch it with another card if necessary.
Update the PCI card to latest driver you can find for it.
Hit windows key+P when you are in Windows with both cards installed. See if it helps any.