Need help with Zip Drive

When I insert a disk into my Zip 100 MB Parallel Port drive, the
comment "please insert a disk into drive D:" comes up,
although the disk is already in there. This happens with only one of
my disks; unfortunately this is the disk that is nearly full and has
years of useful data on it!

When I insert other disks, the drive clicks once; when I insert this
particular disk, it clicks twice as if it is hesitating. As I
mentioned before. the drive reads other disks but not this one.

Is there a way to have this drive read this disk just once so I can
back it up?

If not, and if I have to send the disk out to a Data Recovery company,
what would it cost?

Any help at all would be greatly appreaciated.

Thank you very much!

Cal