DRM free

Spice up the game with mods that completely revamp the game
 
http://forums.civfanatics.com/forumdisplay.php?f=215

Product Features

Platform: PC
    Multiple multiplayer options including the ability to compete with friends via the Internet, play by E-mail modes or compete locally via the Hotseat and LAN modes.
    Includes four classic games: Sid Meier's Civilization IV, Civilization IV: Warlords expansion pack, Civilization IV: Beyond the Sword expansion pack and Sid Meier's Civilization IV Colonization.
    Innovative features in all four games including: Great People, Holy Cities, missionaries, variable game scales, new land, sea and air units, and loads of new civics.
    New scenarios to encounter in each adventure.
    Classic turn-based PC strategy gaming at its best.


Minimum Specifications:

OS:     Windows 2000/XP/Vista
Processor:  1.2 GHz Intel Pentium 4 or AMD Athlon processor or equivalent
RAM:    512 MB RAM
Video:  DirectX 9.0c compatible 64 MB video card with Shader 1.1 Support or better
Sound:  DirectX 9.0c compatible
DVD-ROM:    4x DVD-ROM drive or faster
Hard Drive Space:   3.8 GB free hard drive space
Other:  Internet connection required for online play