I want ideas on a system I'm implementing

A client asked me to setup a system of networked(server based) computers that doesn't accept any removable storage device even CDs. all went well until i reached the technical department;they are mainly conceed with the maintenance of cash register machines, they protested quiet rudely at the implementation i am working on. there argument is that they use the USB ports to coect the machine with the computer for work. my client's argument is he doesn't want unwanted files(movies, po, music etc) to be shared across the network. they have asked me to come up with a plan, any ideas?

here is mine

• to block their computer from sharing files across the network, sadly i dont know how to do this.