Hi,
1) Which game are you trying to play?
2) What is the exact/complete error message you receive when you launch the game?
3) Which version of DirectX is on your computer?
You may refer the following article to check the version of DirectX installed on the computer.
http://windows.microsoft.com/en-US/windows7/Which-version-of-DirectX-is-on-your-computer
Run ‘Windows Update’ to install latest DirectX available.
http://windows.microsoft.com/en-US/windows7/Install-Windows-updates