To know the correct DirectX version installed on your computer:
On the Start menu, click 'Run'.
Type in "dxdiag" to bring up the DirectX Diagnostic Tool.
The DirectX version is listed under the System tab.
In general, DirectX 8.1 comes pre-installed with Windows XP.
DirectX 7.0 comes pre-installed with Windows 2000.
For the latest version of DirectX, please visit:
https://www.microsoft.com/downloads/details.aspx?FamilyID=2da43d38-db71-4c1b-bc6a-9b6652cd92a3&DisplayLang=en.