DirectX Version Checker is a small freeware program to check the DirectX version in Windows. It can check the following information:

DirectX Version;
DirectX Debug Levels;
DirectInput Devices;
DirectShow Filters;
All Video Compressors;
All Audio Compressors

How to check DirectX version?

Using "dxdiag"

In Windows 7, Vista and XP, and probably most other versions of Windows:
Click "Start" button
Click "Run"
Type: dxdiag, and press enter
Look for Direct X version line in the dialog that opens

Using "DirectX Version Checker"

A freeware utilty to check the DirectX version:
Download "directxversionchecker.zip"
Unzip and run program