If you are using Ad-Aware Anniversary Edition Plus or Pro:

Click on the 'update now' button to download the latest Ad-Aware installation file. The link will redirect to the Ad-Aware Free page on Download.com. Note: The installation file for Ad-Aware Free (Ad-AwareInstallation.exe) is the same as for Plus and Pro.

Once downloaded, double click the installation file and follow the installation wizard. At the end of installation your license will be automatically be activated and transfered to Ad-Aware 8.1 .

This is a free update at no extra cost.