A central station distributes software by telephone. The central station accepts credit card information, transmits an acceptance code to a caller and then terminates the call. After verifying the credit card information, the station calls the purchaser back and continues with the transaction only after receiving the acceptance code. The central station then transmits a Control Transfer Program and Initialization Program to the purchaser, and the purchaser executes the Initialization Program to turn over control of the purchaser computer to the central station. The Control Transfer Program is then executed to transfer first a Protection program for ensuring that no memory resident copying programs are running, than a Storing Program for modifying the purchased program for storage at the purchaser computer, and finally the requested program itself. During the transaction, the various transmitted programs are erased, so that at the end of the transaction only a copy protected version of the purchased program remains on the purchaser's disk.