A method and system for protecting software products from unauthorized use and distribution is described. The system comprises a client process executed on a client computer coupled to a producer computer over a network. The method comprises the steps of providing to a user a copy of the distributed software, the distributed software comprising an incomplete executable program requiring a security module to be installed prior to execution on the client computer. The user receives a registration code for use with the distributed software. Upon attempted execution of the distributed software the producer computer requests user registration from the user. Upon receipt of the registration information including the registration code from the user, the producer computer validates the registration code and constructing a security module for transmission to the client computer. The security module is integrated with the distributed software to allow execution of the executable program.