This post is just meant to freshen up everyone’s memory, because I still see (and get) stories (and questions)about backing up a ConfigMgr 2007 Site (and then especially about Secondary Sites). Let’s start with the most important part, the only supported way to restore your site is to use the Site Repair Wizard. This wizard needs a backup that is created with the standard Backup ConfigMgr Site Server maintenance task.
How to back up a Primary Site 
- Open the Configuration Manager console and browse to System Center Configuration Manager > Site Database > Site Management > <YourSiteName> > Site Settings > Site Maintenance > Tasks.
- Select the Backup ConfigMgr Site Server task and click in the Actions pane Properties (or right-click the Backup ConfigMgr Site Server task and click Properties) to open the Backup ConfigMgr Site Server Properties.
- Select Enable this task, specify the backup task properties (like backup destination, day and time) and click Ok.
How to back up a Secondary Site
As you might know there is also a task to create a backup of a Secondary Site. Just keep in mind that it has no use to enable it, because you cannot restore this backup by using the Site Repair Wizard. The only supported way to recreate your Secondary Site is to reinstall your Secondary Site! After reinstalling the Secondary Site, the Primary Site will replicate the site data to it.
More information about Tasks for Backing Up a Site: http://technet.microsoft.com/en-us/library/bb680862.aspx