I assume you are referring to Antivir PE Classic, the free version. I use it on two systems, seems to be very good and reliable.
What's the date of the version you currently have installed?
There's nothing that should be able to change your initial configuration...nothing legal, anyway
Next time you uninstall it...you might also want to do a search on your files and in the registry for any/all "Avira" or "Antivir" files/folders/settings...and delete them (before doing a new install).
To search in the registry, look under the Edit function and use the words described above. Make sure that the cursor is at the top of the registry classes when you start. When it has completely scanned the registry, it will tell you.