These are the official minimum specs

OS: Microsoft Windows XP, Windows Vista and Windows 7 (Windows 95/98/ME/2000 are unsupported)
Processor: Intel Pentium 4 3.2 GHz or AMD Athlon 64 3200+ processor or better supported
Memory: 1 GB RAM
Graphics: 256 MB NVIDIA GeForce 6600GT or better or ATI Radeon 1600XT or better
DirectX: Microsoft DirectX(R) 9.0c
Hard Drive: 12GB of free hard drive space
Sound: 100% DirectX 9.0c compatible sound card
Internet: Broadband connection required for Multiplayer Connectivity. Internet Connection required for activation