Problems with my Motherboard/Graphics card combo

I recently bought a GIGABYTE GA-MA78GM-S2H w/ integrated ATI 3200 HD graphics card.

The mobo works fine while running onboard.

But when I want to use my 8600 GT 512, it will only run SOME games.

The lower end games like Runes of Magic or Titan Quest will cause my computer to do a hard reboot.

No BSOD, as I have already turned off the "automatically restart" feature in Windows.

Any ideas? Should I buy an ATI card to fix this problem?

I'm more concerned about what your video driver situation is...

You state:

It sounds like you might be trying to get these to 'co-exist'; when you added the card, did you uninstall the 'on-board' drivers completely, before installing the card drivers?

In the BIOS:

On the "Advanced BIOS Features" page:

"UMA Frame Buffer Size" to "Auto"
"Init Display First" to "PEG"
"Surround View" to "Disabled"

On the "MB Intelligent Tweaker(M.I.T.)" page:

"PCIE Clock (MHz)" to "100", not auto - auto sometimes doesn't work properly...

If you want to use the Hybrid Xfire, this is the only option; trying to get an ATI and an nVidia to work together is like putting a snake and a mongoose in a box! If you will be happy with the performance of the nVidia alone, with a bit of fiddling, it should work fine...