Jon,
in Enterprise Manager, go to Management then Database Maintenance. Do you have a database maintenance plan in there? Hopefully you do.
In the complete backup, you may well have a backup the database option set. I recommend backing up to disk. Note the folder name that it backs up to (could be set to default directory).
Don't change any of the settings and report on them in this thread (I know its a SQL issue, but we're checking you can take a correct backup). Once that is checked, you can backup the backup folder and you are done.
Now, if the database gets corrupted or whatever, you can restore from the disk backup that the maintenance plan has made. If the server goes completely, you install Windows, SQL server and then restore from tape to the backup folder and restore from the backup folder to SQL.
Trust me - I've used this solution for years!