I was meddling with theme settings the other day and turned of transparency which seemed to disable Aero. Now I cannot seem to turn it back on again. I checked the online help and it sent me to the following
"Under Colors, click Highest (32 bit), and then click OK. (If you can't select 32 bit, check that your resolution is as high as possible, and then try again.)"
Check - OK this is fine
"Click the Monitor tab, and then click a refresh rate that's higher than 10 hertz."
Check - OK
"To change the desktop theme to Windows Vista
Click to open Theme Settings.
In the Theme list, click Windows Vista , and then click OK."
Check - OK
"To change the color scheme to Windows Aero
Click to open Appearance Settings.
In the Color scheme list, click Windows Aero, and then click OK."
Windows Aero is not on the list only Windows Vista Basic, Windows Standard, Windows Classic and some High Contrast ones.
I have checked that I have the latest driver for the Graphics card a Radeon X600
Aero was working fine so I know the paltform supports it - just can't turn it back on again.