Minimum:

Supported OS: Windows® XP/Windows Vista® (only)
Processor: Dual core processor 2.6 GHz Intel® Pentium® D or AMD Athlon™ 64 X2 3800+ (Intel Core® 2 Duo 2.2 GHz or AMD Athlon 64 X2 4400+ or better recommended)
System Memory: Windows XP: 1 GB RAM / Windows Vista: 2 GB RAM
Video Card: 256 MB DirectX® 10.0-compliant video card or DirectX 9.0-compliant card with Shader Model 3.0 or higher (*see supported list)
Sound Card: DirectX 9.0 or 10.0-compliant sound card (5.1 sound card recommended)
DirectX Version: Direct X 9.0 (Windows XP) or 10.0 (Windows Vista) libraries
Hard Disk: 8 GB available hard disk space
Supported Peripherals: Keyboard, mouse, optional controller (Xbox 360® Controller for Windows recommended)
*Supported video cards at time of release: ATI® RADEON® X1600** /1650**- 1950/ HD 2000/3000 series, NVIDIA GeForce® 6800**/7/8/9 series. **PCI Express only supported. Laptop versions of these cards may work but are NOT supported. These chipsets are the only ones that will run this game. For the most up-to-date requirements, please visit the FAQ for this game at: http://support.ubi.com.

Assassin's Creed: Director's Cut Edition screenshots