To determine if DirectX is already installed on the computer,

1. Click on the Start button in the lower left hand corner of the desktop.

2. Click Run and a dialog box will appear, titled Run.

3. In the Open edit box, type in dxdiag and click the OK button. 

4. If a message box appears titled dxdiag saying "Cannot find file....", then DirectX is not installed on the machine (click here for guidelines on 'How to install DirectX').  If a dialog box appears titled, DirectX Diagnostic Tool, then DirectX is installed on the computer.

5. The version of DirectX is displayed at the bottom of the System Information box, under the System tab of the dialog box