It seems that this laptop comes with a variation that includes an AMD Radeon card.
The following link with drivers suggests that:
Go to device manager.
Is there another display adapter with amd radeon driver or a basic vga driver, or a device that shows a yellow triangle warning notification about an unknown device or video controller without driver installed ?
That would suggest that you have an amd gpu as well.
Isn't there any sticker on the laptop case that backs this up, or what do the manual that came with the laptop say ?
gigabyte X58A-UD3R rev.2, core i7 975 3.9ghz (stock voltage), windows 8.1 64-bit, corsair 12gb DDR3 1600mhz 7-7-7-20 RAM, sapphire HD 6990 (stock clocks), coolermaster ultimate 900w PSU.
amd catalyst 14.6 RC2 june23