Setup.exe/drive not ready?

I am installing a 3 part training module on a compact 400+, running nt4, for a fire dept. Two of three modules have installed without incident. When installing the third module into the cd-rom tray (drive d) and try running the the setup.exe, a message box opens to inform me that drive e (zip drive) is not ready. I’ve already checked the .inf file which points to the d: drive.