In addition to the standard PC version, Ubisoft has announced a special "Black Edition" of Assassin's Creed II for $64.99. The press release is incredibly vague about what extras it may contain, simply referring to them as "additional content." An Ubisoft representative remained cryptic about the bonuses, too, promising a "reveal in February," which suggests that the content could differ from the "Black Edition" released on consoles.
Minimum Configuration:
SUPPORTED OS: Windows XP (32-64 bits) /Windows Vista®(32-64 bits)/Windows 7 (32-64 bits)
Processor: Intel Core 2 Duo 1.8 GHZ or AMD Athlon X2 64 2.4GHZ RAM: 1.5 GB Windows XP / 2 GB Windows Vista - Windows 7
Video Card: 256 MB DirectX 9.0compliant card with Shader Model 3.0 or higher
Sound Card: DirectX 9.0 compliant sound card DirectX Version: DirectX 9.0
Hard Drive Space: 8 GB
Peripherals Supported: Keyboard, mouse, optional controller
Recommended Configuration:
Processor: Intel Core 2 Duo E6700 2.6 GHz or AMD Athlon 64 X2 6000+ or better
Video Card: GeForce 8800 GT or ATI Radeon HD 4700 or better
Sound: 5.1 sound card
Peripherals: Keyboard, mouse, joystick optional (Xbox 360 Controller for Windows recommended)
Supported Video Cards at Time of Release: ATI RADEON X1950, HD 2000/3000/4000/5000 series NVIDIA GeForce 7/8/9/100/200 series
http://www.joystiq.com/2010/01/25/assassins-creed-2-pc-specs-date-revealed/