To backup the current system and user profile to C:\Backup (Remember to have created the directory):
This will restore a backup from C:\Backup and files being replaced are placed in C:\Backup.old (Remember to have created the directory):
The restore just renames the file so both the new, backup and destination must be on the same drive. One can also do the restore the registry using the recovery console as the Regback saves the backup in the proper registry file format.
Regrest C:\Backup C:\Backup.old
Note if one don't like command line tools then one can try this very userfriendly utility called EruNT.
More Info MS KB318149