VALVe now sends their gifts to NVIDIA product users. Only with a NVIDIA product installed in your computers and have a steam account, you can get all these games from VALVe by clicking here:

And did you notice the icon in the right side down of the webpage? Seems it means VALVe already joined NVIDIA’s TWIMTBP program! Expecting VALVe games will get optimized for NVIDIA cards.

VALVe’s press release