Gamestop seems to be selling the Steam version, but only the full collection is coming up atm. Strange too...the only expansion they are selling is for XB360. Seems kind of odd. Perhaps selection will change after the release date.
Specifications:
Minimum
Connectivity Requires the Steam client to install and play
Sound DirectX® 8.1 or higher Sound
DirectX DirectX® 8.1 or higher
Hard Drive Space 12 GB Available Hard Drive Space
Operating System Windows® Vista / 7
Processor 800 MHz Pentium® III or faster Processor
RAM 128 MB Available System Memory
Video Card 32 MB GeForce series or Radeon 9000 series Video Card