Developers Valve and hardware creator Nvidia have announced a new promotional partnership, including an offer for a free "extended" Portal demo entitled First Slice exclusively available for PC users with GeForce hardware.

Valve says that its regular Steam Hardware Survey shows that the GeForce graphics hardware is used more than any others, and that the deal is intended to "further support this popular PC gaming configuration."

In contrast to the developer's previous partnership with competing hardware company ATI, the latest release says Valve and Nvidia have "entered into an agreement to collaborate on development, distribution, events, and more."

The free demo deal is the first campaign under the new agreement, and, in addition to First Slice, installs copies of Half-Life 2: Deathmath, Half-Life 2: Lost Coast and Peggle Extreme, the Half Life branded version of PopCap's cult hit casual game.

To get the games, users can visit Valve's Nvidia site, where GeForce hardware is auto-detected and prompts Steam to install the titles.

Said Valve marketing VP Doug Lombardi, "More Steam gamers, including myself, play on Nvidia hardware than any other GPU. That's a testament to the company's long history of innovation and quality. By working together with Nvidia to expand our development, distribution, and marketing efforts, we're increasing our ability to serve the millions of Nvidia customers logging onto Steam and help us prepare for our next generation of content."