Windows Complete PC Backup is an image based backup tool where you could take a backup of your entire system and restore it later. Currently in Vista, the backed up image cannot be saved in a network share as in Windows Home Server. This requires to write the backup to DVD(s) or to an external hard drive.
With Windows 7, Long has discovered one can directly backup to a network share! I guess now's a good a time as any to buy a NAS device. :)