1. A method of controlling the use and replication of diskette software contents on unauthorized diskette-driven computing systems, said method comprising the steps of: placing a first ID code in a preselected computing system; identifying a source of programming software for said computing system with a second ID code; placing said second ID code on a diskette bearing a program obtained from said source, said program including a execution protection feature; deriving a first check number through encryption of one of said ID codes with the other of said ID codes; placing said first check number on said diskette; and upon access of said diskette by any computing system, deriving a second check number through encryption of said second ID code on said diskette with an ID code in said accessing computing system, comparing said second with said first check number, and bypassing the protection feature in the event of a match.