Minimum requirements:

OS: Windows XP (with SP3), Windows Vista (with SP2), Windows 7 (with SP1), Windows 8 (32bit and 64bit for each OS)
Processor: Intel Core 2 Duo E6400 @ 2.53Ghz or AMD Athlon64 X2 5600+ @ 2.8Ghz
RAM: 2 GB
Video Card: 512 VRAM DirectX 10 with Shader Model 4.0 (see supported list**)
Hard Drive Space: 25 GB or more
Sound Card: DirectX 9.0c Compatible Sound Card 5.1 with Latest Drivers
Peripherals: Windows-compatible keyboard and mouse required. Optional controller: Razer Onza, Logitech F310, Logitech F510 Rumble, Logitech F710 Wireless, Saitek Cyborg P3600, Xbox 360 Controller

Recommended configuration:

OS: Windows XP (with SP3), Windows Vista (with SP2), Windows 7 (with SP1), Windows 8 (32bit and 64bit for each OS)
Processor: Core 2 Quad Q8400 @ 2.6Ghz or Phenom II X4 940 @ 3.0Ghz recommended
RAM: 4 GB
Video Card: 1024 VRAM DirectX 11 with Shader Model 5.0 or higher (see supported list**)
Hard Drive Space: 25 GB or more
Sound Card: DirectX 9.0c Compatible Sound Card 5.1 with Latest Drivers
Peripherals: Windows-compatible keyboard and mouse required. Optional controller: Razer Onza, Logitech F310, Logitech F510 Rumble, Logitech F710 Wireless, Saitek Cyborg P3600, Xbox 360 Controller

** Supported video cards at time of release:
Laptop models of these desktop cards may work as long as their performance is on-par with the minimum configuration.