Issue in NT Backup

I am using Win2003 Std Ed with sp2. DAT72 Tape Drive is connected wiith the

pc. I have taken some backup using NTBackup utility that consumes 4 tapes and

checked the media lable was found for the backup job.

After 15 days (yesterday) I wanted to restore some files from the backup and

checked the media lable was not found. I thought somebody could have deleted

the media lable.

I inserted the first tape into the tape drive and added the media to the

existing catalog. After that it shows the media as "offline". When I insert

the tape it recognised and shown the tape drive with offline status.

Please guide me to bring the media offline to online.

I have searched and followed some instructions on net but no luck.

Shanthi