You can set it to remind you every x days upon closing Outlook (where x is
configurable). You cannot schedule this as Outlook needs to be closed in
order to backup the pst-file correctly. If a backup attempt is made while
Outlook is still running, the backup will fail since the pst-file is locked.
If you were to close Outlook and then schedule the backup via Windows's
Scheduled Tasks, then you can suffice with a simply copy command. You can
find an example for that and additional solutions (like backup add-ins which
have a scheduling function built-in) at the bottom of this article;
http://www.howto-outlook.com/howto/backupandrestore.htm
