At 07:11 PM 3/12/98 -0500, you wrote:
>Anyone out there experience some grief with a ZIP drive. I have a disk here
>that locks up the system once 50% of the disk is used. If I keep it under
>50% it works, no knocking sound. If it's over 50% it knocks!
>
Sounds like a bad disk rather than a problem with the drive.  Have you
tried doing a full reformat of the disk?  Some of these disks have a
life-time guarantee.  You might want to check on that.