I wanted a 2nd vid card to multi-task better,
so i take a card from an older pc and stick it in (after powering off the computer and removing all cables), i already installed video cards before, but never a 2nd one
I boot up, go in DEVICE manager to check if windows detects it;
it didn't detect my 2nd one, it detected my 1st one, but now it has ERROR and didn't give it ressources
both my GPU's fans were working, but only my main GPU would display something when I'd plug the monitor in it.
So i decided to remove the 2nd gpu and cold reboot, main gpu would still not get resources therefore i couldn't play 3d video games (Minecraft gives me OpenGL error, and it's a game i play on a weekly basis with never an error).
So i reinstalled drivers and rebooted and now i can use my main gpu, but I'd really like help on understand what happened and/or help on getting my 2nd video card working...

specs:
mobo: asus M4A79XTD EVO
main vid card: radeon 6670 1gb
2nd vid card: radeon x600 PRO 256(?)mb

Thanks for reading.Does the 2nd video card work properly on its own, when your main graphics card is not inserted?

"Resources"... the first thing that comes to mind is a possible IRQ conflict...
As a quick fix try to clear your CMOS and try again with both video cards inserted so hopefully the BIOS will reconfigure itself... Also when you boot your computer up make sure that your second video card is connected to something so it will be marked "active" in Windows.

Also, I NOTICE that the Radeon X300-X1950 series have a different set of drivers from the Radeon HD series.
To Windows they seem like graphics cards from two different manufacturers; installing two different sets of video drivers won't go WELL from my experience.