Mi sa che č proprio la x800gt e i driver per questa (anche x600 pare) che non fanno andare aero
http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=1148379&SiteID=1
citazione da un forum :
The problem seems to be an ATI driver's problem. To solve it a run AERO intall the old version of Catalist drivers for windows Vista RC1. This is the only driver that make aero works if you have an x800GT. I have tried RC2, RTM and final drivers (7.1) and aero does not work. It works with RC1 drivers.
RC1 drivers does not have native OPEN GL support so not all the games works with these drivers. I hope ATI solve it soon.
Infine qua :
Wiki
Nella sezione schede video :
Radeon X600: Drivers provided with Windows work fine. All of Aero GUI works fine.
Quindi per chi come me avesse problemi con aero, mi sa che l'unica č aspettare driver aggiornati a questo punto