For those of you running with a 64-bit capable AMD processor, along with the Windows® 64-bit operating system, Half-Life 2 and Lost Coast are now available in native 64-bit versions. Steam will automatically detect your OS and run the appropriate version the next time you run these games.

We've been working with AMD to get the Source engine up and running in 64-bit mode to make sure we're taking advantage of these hardware configurations. This is just a first step for Valve into 64-bit. Going forward, we realize that more and more of our customers will be running with 64-bit processors and we will be set to take true advantage of them.