I'm out of the office now, but if I recall, it has a setting to hide antivirus related software because they should not be uninstalled with any kind of third party uninstaller. That's because any security related software such as antivirus are protected against unauthorized uninstallation (otherwise, any malware running in the computer could simply just uninstall your antivirus).
So, you should uninstall Avira by using Avira's own uninstaller. If that fails, you should contact Avira for support. Using any third party uninstaller is not recommended.
