One way to manage backing up and restoring SharePoint 2003 is to use a third party tool like this one from AvePoint. However, I've just written up instructions on how to schedule regular backups automatically yourself. You'll find it here.

SPSFAQ050217 - Are there any programs for backing up SharePoint 2003?
SPSFAQ050216 - How can I do backups of SharePoint 2003 and even schedule then to run automatically?