If the installation script of Avira AntiVir reports that the installation of LSP (Layered Service Provider) failed, LSP has to be reset. It may happen, if WebGuard or MailGuard is installed, along with another LSP-based program on the same computer.
To reset the LSP on Windows XP:
To reset the LSP on Windows Vista/ Windows 7:
After the restart, you can continue installing Avira AntiVir.