General instructions are as below. (A note: I have found it's easier to uninstall if you first disable the Ad-Aware "service" that lies in the "services.msc" location.):

Uninstall Ad-Aware 2008
You can use one of the methods below to uninstall Ad-Aware 2008.

Uninstaller
Go to the ?Lavasoft Ad-Aware 2008? folder in your Start menu.
Run ?Uninstall Ad-Aware 2008?.
Verify uninstalling by selecting ?Yes.?
When the program exits,Ad-Aware 2008 has been uninstalled.

Control Panel
Go to the Control Panel.
Run ?Add or Remove Programs?.
Select Ad-Aware 2008 in the list and click the ?Change/Remove? button
Verify uninstalling by selecting ?Yes.?
When the program exits, Ad-Aware 2008 has been uninstalled.

If you still get the error and Ad-Aware won't uninstall, try a different tool such as the Windows Installer Cleanup Utility below:

http://support.microsoft.com/kb/290301

Hope this helps.

Grif