The Tarma Installer is a tool for developers to distribute their software. So this is a False Positive. And specifically, it is the _Setupx.dll file that is being detected. This file is accessing privileged areas of the system to perform the install, so that's why it is being flagged as a "Potentially dangerous object".
Please submit the _Setupx.dll file file as described in the top section of this Post: Handling False Positive, hopefully the AVG data base will be updated.
If your not a developer, you should be able to perform a standard Program Remove to delete the package from your system. If you are using this software, then you will need for AVG to add this file to their exceptions list.