For windows 7:
open control panel, go to programs and features and check "Turn on or off Windows features" and check "games"
Log on as Administrator or as a member of the Administrators group.
Click Start, click Control Panel, and then double-click Add or Remove Programs.
Click Add/Remove Windows Components. The Windows Components Wizard starts.
In the Components list, click to select the check box that is next to the component that you want to add. If the check box for a component is shaded, only some of its subcomponents are selected for installation.
Please always add as much information about your PC that you can so we can give you a more accurate answer.