A few comments were posted a while back with people looking for Backup solutions for their Windows Mobile 5 Pocket PC's. 

Sunnysoft have their Backup Manager product which now supports Windows Mobile 5!

Backup Manager

http://www.sunnysoft.cz/en_clanek.php?clanekid=51

Sunnysoft Backup Manager enables:

 Backup to desired location including memory cards
 Selective backup
 Backup of files stored on memory cards
 Automatic backup according to custom schedule
 Automatic backup according to battery status (drain)
 Create selfextracting backup file
 Backup compression
 Backup password protection
 Operate the program by entering commandline parametes (manual will be available later
 A choice of backup method more convenient to you - Basic mode or Advanced mode
 Store you backups to a Desktop PC automaticaly
 XML configuration file support (on demand)
 Turn off reset confirmation dialogs if needed