If you have used the Windows Backup application before in other Windows Server versions, you know that it is called NTBACKUP and you can run it, using that command, from the command line. If you attempt the same command in Windows Server 2008, you will find that you get an error. This is because the new Windows Server 2008 Backup program is called Windows Server Backup.
To install Windows Server Backup, go to Start -> Administrative Tools -> Server Manager. From there, click on Features, then Add a Feature. You want to add the Windows Server Backup. This will get your CLI telnet application working again if you just type “backup” instead of NTBackup.
Also see this tutorial which will probably answer your question in more detail: