Install and play
No problem out there anf no need for a Games folder on c. Just install wheere you want. Typically I let everything concerning games installing standard location as you never now, what happens in the future with some game patches, addobs, etc.
But I think you have enough knowledge about windows to do what you want.
I would have liked to see a ati user, but 670 should run well enough except some stutters of the weak memory interface of nvidia. Noted that before: Can be a problem, but in most games not, although it is nice to have a good interface in the future for engines with high texture loads like cry engine can do. But for now you are fine and as ling as game developers have to program bad games for bad working consoles, you will never have a problem.
Considering that it is not that wrong!