The only way I can back up is if I set the overwrite protection to none.
How do I set partial protection? This is how I try to do it:

go to tools/option/overwrite, set that to partial
then on the media tab set the media group to a specific number of days or

I do that above but when I insert a tape that has been erased and try to
backup I get this:
(alert: Please insert overwritable media)
I have to set overwrite to none to get it to back up.

What am I doing wrong?