Valve announces a 10% preorder discount for Left 4 Dead for both Windows and Xbox 360, confirming yesterday's revelation of early demo access for those who preorder. The most interesting part of the announcement is word that the demo will only run for two weeks for those who preorder and one week for those who don't, saying: "The demo concludes on November 18, when Left 4 Dead will be made available at retail outlets across North America and worldwide via Steam." Here's the deal:

October 24, 2008 –Valve, creators of best-selling game franchises (Half-Life, Portal, Team Fortress, and Counter-Strike) and leading technologies (Steam and Source), today announced a special promotion granting those who pre-order Left 4 Dead early access to the official demo.

Left 4 Dead is the new survival action game from Valve that blends the social entertainment experience of multiplayer games such as Counter-Strike and Team Fortress with the dramatic, narrative experience made popular in single player action game classics such as the Half-Life series of games.

Early access to the demo begins Thursday, November 6 on both the Xbox 360® video game and entertainment system from Microsoft and PC. This pre-order promotion applies to all Steam PC pre-orders and all Xbox 360 and Windows-based PC pre-orders from participating retailers in North America. The demo will feature single player and co-operative modes, supporting 1 to 4 player games.

On November 11 the demo will be made available to all Xbox 360 and PC and gamers, with no obligation to purchase. The demo concludes on November 18, when Left 4 Dead will be made available at retail outlets across North America and worldwide via Steam.

This pre-order promotion is scheduled in concert with the previously announced $10 million consumer launch campaign that spans television, outdoor, print, and online advertising.

“Every time someone plays Left 4 Dead, we witness the most overwhelmingly positive reaction that we’ve seen from any of our games,” said Gabe Newell, president and co-founder of Valve. “This gives us tremendous confidence in the product and why we’ve taken the game on the road, produced this pre-launch demo, and invested more advertising dollars on the title than any prior release from Valve.”

Playable in single player, co-operative, and multiplayer modes, Left 4 Dead is one of the most anticipated releases of 2008 and winner of numerous pre-launch awards, including Best of E3 from multiple outlets.

For more information, please visit L4D.com or www.steamgames.com