If you have a video card that is using WDDM drivers and supports DirectX 9c but is not allowing you to use vista glass, there is a cool trick that you can use to force Aero to run. Follow the steps below:

Click on the start button and key in regedit and hit Enter.
Navigate through, HKEY_CURRENT_USER, Software, Microsoft, Windows and DWM.
Set Composition to 1 and CompositionPolicy to 2.
Restart the DWM by restarting the Desktop Windows Manager Session Manager service. This can be done in services.msc or by typing net stop uxsms and net start uxsms at command prompt.
Once the service restarts you will have glass!