The minimum specifications will allow you to scrape through at the lowest possible graphics settings. In my experience, this never provides a reliable gameplay and things like over-populated areas will cause your system to slow completely down, and even to crash.
CPU: Intel Core 2 Quad 2.4 GHz Processor or equivalent
CPU: AMD Phenom II X3 Triple core 2.8 GHz or equivalent
RAM: 4GB to 8GB Vista and Windows 7
DirectX 11 Video: ATI 5870 or greater
DirectX 11 Video: NVIDIA 480 or greater
This type of setup is getting us 60FPS +
Official PC Minimum:
OSWindows XP, Vista/7
CPU: AMD Athlon 64 X2 Dual-Core 4000+ or better · Intel Core 2 Duo Processor 2.0GHz or better
RAM: Windows XP: 1.5GB · Windows Vista and Windows 7: 2GB · PCs using a built-in graphical chipset, 2GB RAM recommended.
VideoATI X1800 or better* · nVidia 7800 or better* · Intel 4100 Integrated Graphics or better*
Disc Drive: DVD ROM drive required
Hard Drive: 25+ GB
If you have any questions please post in the comments section below!