Well the 7970m is made by AMD and the GTX 670 is made by nVidia. Sorta like a Ford/Chevy kind of thing. Both make GPU's and they compete against each other.Here is a comparison of the AMD 7970m and the GTX 680 (one step up from the GTX 670).
It'll give you an idea of what kind of performance you might see with those GPU's. Some of the GTX 670 is on the list too, but it's in limited supply.
The Windows OS is the "Windows Operating System" is the software that runs your system. The laptop I linked comes with the Windows OS already installed. The other laptop doesn't come with it, unless you want to pay more to have it installed.