We’ve covered how to register your Avast Free antivirus to get one year free license key, if you’ve installed and using Avast free antivirus in your Computer, if you purchased or got Avast Pro Internet Security license through a promotion, then without the need to uninstall Avast free and install Pro AV/IS to activate it, you can directly upgrade from Avast free to Pro AV/IS, here is how.

Upgrading from Avast Free AV to Pro AV/Internet Security

1. Open Avast user interface.

2. Click on Settings>Registration

3. Avast Settings window for registration offers options to ‘Insert activation code‘ and ‘Insert license File

Insert Avast activation code or license file

4.  Select Avast license file you’ve downloaded earlier, or use the activation code sent by Avast to your email for upgrade

5.  Avast shows license file info with details such as license folder name, product name and product validity period and asks you to insert the license file.

avast license key

6. Click “Yes”.  If if all goes well for you, you’ll get “ your license has been successfully inserted” message and Avast automatically downloads necessary files and prompts for Computer restart.

7.  After restart, you’ll be using Avast Pro AV/Internet security.

Note: If you’ve Avast Pro AV/IS setup file available, then its better to perform clean install by uninstalling Avast free. Use the above method otherwise, if you don’t have Avast Pro/IS setup file.

Update: This article has been updated to reflect UI changes in Avast 2014.

If you’ve any doubts, ask me in the comments, happy to help.