One time installation floppy disk

I am using a program that comes with a floppy disk that you must put in when installing the program.I would like to copy the floppy disk so i can have it for a backup in case of disk failure the company wants 75.00 for a new disk..Here is the problem after you use the floppy once it is no good anymore.Even with the floppy locked something is writing to it how is this possible?I now have a new floppy key and would like to back it up before i install but i know windows can change things too evn just by opening a floppy