Here are a collection of retrospect tutorials made available from the Retrospect website and copied here for easy access.
(For SP2 and later)
When you install Windows XP Service Pack 2 (SP2), the service pack automatically enables a firewall on the computer running SP2. This firewall can interfere with the execution of backups from a Retrospect client computer to a Retrospect backup computer.
If you already have XP Service Pack 2 installed, before installing the Retrospect client software, then the installer will automatically adjust the Windows firewall settings for you. But, if you install SP2 after the Retrospect client, then you need to make these changes yourself.
To adjust settings on a Retrospect client computer