Those of you who purchased Left 4 Dead on the PC thinking you'd save yourself money on downloadable content were wrong: the upcoming Survival Pack is free for both the Xbox 360 and PC versions.

It's not immediately clear how it's free on the Xbox 360, given Microsoft's love for money. It could be that there's some sort of sponsorship deal in place here.

The Survival Pack, due this spring, adds Versus Mode support for Death Toll and Dead Air Campaigns, as well as a new Survival mode. The release of the downloadable content will coincide with the release of a Critic's Choice Edition to stores, which includes the original retail game as well as the new DLC.