Minimum System Requirements
Windows
OS:
Windows XP SP3
Processor:
2.4 GHz Dual Core Processor
Memory:
2 GB RAM
Graphics:
NVIDIA GeForce 8600 /ATI Radeon HD 2600
Storage:
2 GB available space
Notes:
Version 9.0; Initial installation requires one-time internet connection for Steam authentication; software installations required (included with the game) include Steam Client, DirectX 9, Microsoft .NET 4 Framework, Visual C++ Redistributable 2010, and AMD CPU Drivers (XP Only/AMD Only)
These are the requirements the publisher lists on Steam.
