here is a small utility i wrote a while back when I was having aero problems with my other laptop.. the option to turn it ON didnt always appear for me. so this uses window's services to attempt to force it on/off.
when you run it, the utility will simply turn Aero OFF if its on.. and then turn it back ON.. (hence the name, Aero Restart)
it will also accept command line params: "/on" and "/off" to force one way or the other..
here's what it actually does to attempt to turn it on:
RegSet HKEY_CURRENT_USER, "Software\Microsoft\Windows\DWM", "Composition", "1"
RegSet HKEY_CURRENT_USER, "Software\Microsoft\Windows\DWM", "CompositionPolicy", "2"
Call ServiceStart( "uxsms")