Verified answer

Right click on the desktop and choose "Personalize". Then click on "Windows Color and Appearance". Now put a check mark in "Enable Transparency".

windows aero starts with vista by default, so if it's not starting then then your computer probably can't handle it as it has quite steep requirements... also not all Vistas have Aero... for example if you have Vista Home Basic then Aero is not installed on yor computer... go to properties, themes i believe and see if it says "vista basic" or if you can select "vista" theme, i dotn rememebr exactly as I'm at work right now... XP here...