Standard users cannot configure or perform file backup in Windows Vista Backup and Restore Center
Windows Vista Backup and Restore Center requires the user to have administrator-level permissions to configure or run a backup on the local computer. By default, standard users are not permitted to configure or run a backup because they have restricted access to resources on the local computer. Most enterprise users may have alternative file backup solutions that are provided by their IT organization. However, if standard users of the local computer are required to back up personal files in Windows Vista, they may choose to download Microsoft Windows NT Backup for Windows Vista. Windows NT Backup is a supplemental utility for Windows Vista.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB955637.