What is going on here?

My zip drive will not reconize any disks’ that I insert into the drive. It pops up a diolog box saying please insert disk into drive. I just installed a replacement zip dirve and it keeps doing the same thing. Please insert disk into the drive. I have tryed more than one disk too. I have updated the drivers, I have check the EDIE and power cables too. I am lost at this point. Any information would be great. I am using windows 2000 pro and windows 98, it will do it on both sides of the operatingsystems.