Hard Disk Space
"Civilization V" requires at least 8 GB of free hard disk space for installation. You may need to purchase an additional hard drive or run a disk defragmenter on your current one to free up some space if you have under 8 GB available.
RAM
The minimum amount of RAM required to run "Civilization V" is 2 GB. This is enough to load the game, but 4 GB is recommended for best performance.
Video
A 256 MB nVidia 7900 GS or a 256 MB ATI HD2600 XT or any video card equal to or better than these are needed to meet the minimum requirements. 512 MB video cards are recommended for players who want the best performance possible.
Operating System
The oldest OS you can use to run "Civilization V" is Windows XP with Service Pack 3 installed. Anything newer than XP with SP3 will run the game. For best performance, Windows Vista with Service Pack 2 installed or Windows 7 is recommended.