Two users - one box

I have a customer with a nil budget. He has an existing box with all the software he will ever need. He wants to add another user to his office but not buy another box and he doesn't want to buy another set of software licences. I remember, somewhere, about a piece of kit that would allow two users to use one box, two monitors, two keyboards, two mice and working in different parts of the system. I've tried a reverse KMV switch and that just allowed both monitors to see the same image. Has anyone any ideas?

Steve