The most recent Steam Hardware Survey shows more Steam gamers play on NVIDIA GeForce hardware than any other graphics platform. In an effort to further support this popular PC gaming configuration - Steam games plus NVIDIA hardware - Valve and NVIDIA have entered into an agreement to collaborate on development, distribution, events, and more.
Effective immediately, all NVIDIA gamers may receive a free copy of Portal: First Slice, a special version of the award-winning new game from Valve, by visiting http://www.steamgames.com/nvidia
and Taking the test. Steam will then auto-detect the presence of NVIDIA hardware and make Portal: First Slice available immediately, free of charge. To make it easy for all NVIDIA customers to redeem this offer, a link to the Steam offer will also be included in all NVIDIA drivers.http://www.steamgames.com/nvidia
NB this is a new "extended" demo version of the full Portal game, not the full version itself.