The ntbackup command is not available in Windows Vista or Windows Server 2008. Instead, you should use the wbadmin command and subcommands to back up and restore your computer and files from a command prompt.
You cannot recover backups that you created with ntbackup by using wbadmin. However, a version of ntbackup is available as a download for Windows Server 2008 and Windows Vista users who want to recover backups that they created using ntbackup. This downloadable version of ntbackup enables you to perform recoveries only of legacy backups, and it cannot be used on computers running Windows Server 2008 or Windows Vista to create new backups. To download this version of ntbackup, see http://go.microsoft.com/fwlink/?LinkId=82917.