Minimum:

OS: Windows XP, Vista, or 7
Processor: Dual core CPU (any Core 2 Duo or better)
Memory: 1GB RAM
Graphics: DirectX 9, Shader Model 3 compliant graphics cards (GeForce 8800, GeForce GT220 and above)
DirectX®: DirectX 9.0c

Recommended:

Processor: Any Quad Core or 3.0+ GHz Dual Core CPU
Memory: 2GB RAM
Graphics: DirectX 10 compliant graphics card (GeForce GTX 260 and above)
DirectX®: DirectX 10 or higher

Optimum Requirements:

Processor: Core i7 CPU
Memory: 8GB RAM or higher
Graphics: NVIDIA DirectX 11 compliant graphics card (GeForce GTX 480 and 470)
DirectX®: DirectX 11