Minimum:

Intel Pentium 4 2.0Ghz / AMD Athlon XP 2000+ processor
512MB system RAM
100% DirectX 9.0c compatible 64MB video card with latest manufacturer drivers (see supported chipsets below)
100% DirectX 9.0c compatible 16-bit sound card
2.2GB of uncompressed free hard drive space
Microsoft Windows 2000 or XP with latest service pack installed
DirectX 9.0c (included)

Recommended:

Intel Pentium 4 2.5Ghz / AMD Athlon XP 2500+ processor
1GB system RAM
ATI Radeon X800 series or higher video card with latest manufacturer drivers
Creative Sound Blaster X-Fi series sound card
Broadband internet connection or LAN required for multiplayer

Supported Video Card Chipsets:
ATI Radeon 9600 series
ATI Radeon 9700 series
ATI Radeon 9800 series
ATI Radeon X300 series
ATI Radeon X550 series
ATI Radeon X600 series
ATI Radeon X700 series
ATI Radeon X800 series
ATI Radeon X1300 series
ATI Radeon X1600 series
ATI Radeon X1800 series
ATI Radeon X1900 series
or better with latest manufacturer drivers

NVIDIA GeForce3/Ti series
NVIDIA GeForce4/Ti
NVIDIA GeForce FX 5800 series
NVIDIA GeForce 5900 series
NVIDIA GeForce 6200 series
NVIDIA GeForce 6600 series
NVIDIA GeForce 6800 series
NVIDIA GeForce 7300 series
NVIDIA GeForce 7600 series
NVIDIA GeForce 7800 series
NVIDIA GeForce 7900 series
or better with latest manufacturer drivers