Windows Vista Areo theme stopped working!

Make sure the theme service is still running:

• Start > Run > 'services.msc'
• Scroll down the list and find 'Theme'
• Restart it by clicking the link on the left

If this doesn't bring Aero back then you'll need to re-select the theme:

• Right click on the desktop and choose 'Personalize'
• Choose 'Theme'
• From the drop down list, click 'Browse' and go to 'C:\Windows\Resources\Themes'
• Choose 'aero.theme'

You should be back in business!