Registry Edit Tweaks to Enable Transparent / Aero User Interface in Windows 7
- Type regedit in RUN dialog box and press Enter. It'll open Registry Editor.
- Now go to following key: HKEY_CURRENT_USER\Software\Microsoft\Windows\DWM
- In right-side pane, change value of "Composition" to 1 and "CompositionPolicy" to 2. If you don't see the keys, create them manually using right-click options.
- Restart your system and you'll be able to select the Aero theme from Desktop Properties.