Instructions
Click "Start."
Click "Control Panel."
Click "Programs" and "Programs and Features."
Click on any trial versions of either "Age of Empires III" or "Age of Empires III: The War Chiefs" and select uninstall.
Download Windows Installer 3.1 from the Microsoft Download Center (see Resources). The file is called "WindowsInstaller-KB893803-v2-x86.exe."
Double click on the executable file and follow the installation instructions, agreeing to any Terms and Conditions and maintaining the default settings. Click "Finish" to complete the installation.
Run Windows Installer and click "Windows Install Clean Up."
Select "Age of Empires III: The War Chiefs" from the list and press "Remove."