Do you get the "Would you overwrite the medium" at the begining or the end of the job? If at the end, it sounds like the tape may be filling up
If you follow Chico's advice, any tape that is mounted will be overwritten. I prefer to set the OPP (Overwrite Protectio n Period) so that when you reuse the tapes, they have expire. or when you mount the tape, inventory, then drag it to the SCRATCH media set
As for the Remove Tape Prompt, you can make a registry change to autorespond. See http://seer.entsupport.symantec.com/docs/192055.htm
But I do agree with Chico. You NEED to upgrade to a newer version