In case you plan on doing an in-place upgrade from Windows 7 to Windows 8 it's highly recommended to remove Avira before upgrading because otherwise you will encounter issues, including BSODs. If you have already upgraded to Windows 8, the only way to uninstall Avira is through a manual removal because the automatic removal tools will result in a system crash. Details on how to manually uninstall the software can be found at Avira's Knowledge Base.
Windows 8 introduces significant changes to the operating system platform. As with any new computer operating system, it is possible that some existing software is not compatible with it.
Currently, the Avira products are not ready for Windows 8 and Windows Server 2012 (Built on Windows 8).
Avira is working closely with Microsoft to achieve compatibility for the products as soon as possible. Therefore, it can be said with certainty that the Avira products will be compatible with Windows 8 in the first quarter of 2013.
Avira created a setup page, that will be called up any time a user attempts to install one of our products on Windows 8 or Windows Server 2012 (based on Windows 8).
If an upgrade or a new installation of Windows 8 has already been performed, then the current Avira version can only be uninstalled manually.