GTX 560 installed, slow downs?

[SkaarjMaster]

My brother installed a new video card (PNY GTX 560) in his computer replacing an ancient ATI 9600 Pro and he uninstalled ATI drivers and reinstalled Nvidia drivers and now he has system slow downs. Windows Vista takes longer to boot up and shut down and he has trouble with his sound editing programs taking too long. His system is about 3 years old and he has the same Gigabyte MB as I do as well as an Enermax 720W PSU and he said the video card was hooked up correctly. Any ideas what could be wrong? Is there a video card setting in the bios that he missed?

EDIT: the only video settings in the bios I see are PCI Express Frequency (with a default/auto of 100MHz and other settings from 90-150) and PCI Express Clock Drive (with default/auto of 900mV and other settings of 700, 800 and 1,000).

EDIT AGAIN: not sure if this is the regular or Ti version, but I guess besides thorough video driver uninstall in safe mode and reinstall I guess he could try lowering the clock to 800MHz and see what happens (he's not playing games on it or heavy video editing).

[zirik]

it might be a defective video card. did your brother check to see if there are left over ati software like the notorious ati driver update that runs in the background?

[<RuReady>]

I'm a little confused here.
You say your brother installed a new video card (PNY GTX 560) Which is PCI-E. Replacing an ancient ATI 9600 Pro Which is AGP. In the same MB?