Problem with zip 100 drives in Windows N

I have been having problems installing Iomega Zip 100 drives in Windows NT 4 Workstation. I work in a school district in which the administration hard drives are all partitioned into 3 drives C: D: E: when the drive is installed it re-letters the drives
and leaves the zip drive un re letterable… I have gotten the drive lettered one time only and had to resort to ghosting this particular user’s machine.