Featuring two levels from the first of the game's four acts, the Xbox 360 demo is now available to download from the Xbox Live Marketplace and supports online play for up to four players. It was released last week to GameStop pre-order customers.

The PC demo, meanwhile, is available via Valve's digital distribution client Steam, and arrived roughly 150 minutes late, according to a now-removed countdown on the L4D Steam community group page. Much like the Xbox 360 demo, the PC version hit last week for those that had pre-ordered the game from GameStop or Steam.

The full version of Left 4 Dead hits PC and Xbox 360 on November 18.