Open your registry and browse to the following:

HKCU-Software-Microsoft-Windows-DWM-Composition
Set this to 1.

HKCU-Software-Microsoft-Windows-DWM-Composition-Policy
Set this to 2.

Unless you reboot, you'll have to take one more step and restart DWM by opening
 the command prompt (must "run as" administrator) and type the following:

'net stop uxsms'

'net start uxsms'