After receiving a license file for your AntiVir software, you should save a copy of the HBEDV.KEY on an external data support, such as an USB-stick or an external hard disk. In case you wish to save the license of an installed AntiVir programm, you can find the license file HBEDV.KEY in the AntiVir installation directory.
As long as you did not perform a custom installation, the license file is located in one of the following directories depending on the AntiVir software:

C:\Program Files\Avira\AntiVir PersonalEdition Premium\
C:\Program Files\Avira\Avira Premium Security Suite\
C:\Program Files\Avira\AntiVir Workstation\

You can copy the license file from these directories to another drive, using Windows Explorer or your Desktop.