Livré sous forme de binaire depuis SourceForge, il suffit de décompresser le zip dans un répertoire dédié créé pour l'occasion (au hasard, c:\program files\hobocopy) et il s'utilise ensuite en ligne de commande (il est d'ailleurs plus souple d'ajouter le répertoire dans le PATH histoire de simplifier son usage.

Le petit "a propos" du programme :

HoboCopy (c) 2006 Wangdera Corporation. hobocopy@wangdera.com

Usage:

hobocopy [/statefile=FILE] [/verbosity=LEVEL] [ /full | /incremental ]
         [ /clear ] [ /skipdenied ] [ /y ] [ /simulate ] [/recursive]
         <src> <dest> [<file> [<file> [ ... ] ]

Recursively copies a directory tree from <src> to <dest>.

/statefile   - Specifies a file where information about the copy will
               be written. This argument is required when /incremental
               is specified, as the date and time of the last copy is
               read from this file to determine which files should be
               copied.

/verbosity   - Specifies how much information HoboCopy will emit
               during copy. Legal values are: 0 - almost no
               information will be emitted. 1 - Only error information
               will be emitted. 2 - Errors and warnings will be
               emitted. 3 - Errors, warnings, and some status
               information will be emitted. 4 - Lots of diagnostic
               information will be emitted. The default level is 2.

/full        - Perform a full copy. All files will be copied
               regardless of modification date.

/incremental - Perform an incremental copy. Only files that have
               changed since the last full copy will be copied.
               Specifying this switch requires the /statefile switch
               to be specified, as that's where the date of the last
               full copy is read from.

/clear       - Recursively delete the destination directory before
               copying. HoboCopy will ask for confirmation before
               deleting unless the /y switch is also specified.

/skipdenied  - By default, if HoboCopy does not have sufficient
               privilege to copy a file, the copy will fail with an
               error. When the /skipdenied switch is specified,
               permission errors trying to copy a source file result
               in the file being skipped and the copy continuing.

/y           - Instructs HoboCopy to proceed as if user answered yes
               to any confirmation prompts. Use with caution - in
               combination with the /clear switch, this switch will
               cause the destination directory to be deleted without
               confirmation.

/simulate    - Simulates copy only - no snapshot is taken and no copy
               is performed.

/recursive   - Copies subdirectories (including empty ones). Shortcut: /r

<src>        - The directory to copy (the source directory).
<dest>       - The directory to copy to (the destination directory).
<file>       - A file (e.g. foo.txt) or filespec (e.g. *.txt) to copy.
               Defaults to *.*.

Destiné initialement à la sauvegarde de répertoire complet, la liste des paramètres permet néanmoins de sauvegarder un fichier unique en spécifiant son nom :

"c:\program files\hobocopy\hobocopy.exe" c:\source    c:\destination    fichier-verrouille.dat

Ce qui donne

HoboCopy (c) 2006 Wangdera Corporation. hobocopy@wangdera.com

Starting a full copy from c:\source to c:\destination
Copied directory
Backup successfully completed.
Backup started at 2009-04-27 12:50:49, completed at 2009-04-27 12:52:06.
1 files (586.20 MB, 1 directories) copied, 116 files skipped

Enfantin et tout à fait fonctionnel... En outre, je sens que je vais aussi le tester pour la sauvegarde des photos sur disque externe :-)

Pour les curieux, HoboCopy se base sur Shadow Copy, une possibilité de XP (et des Windows suivant) de créer un image temporaire d'un fichier ou d'un disque et d'en permettre la lecture pendant que les applications accèdent au fichier original.