Setting up a multiseat configuration
I haven't tried it but how about this http://www2.userful.com/products/downloads/free-2-user
As a solution that works for any OS, this gaming.SE answer provides an excellent method: Use VMWare Player to virtualize the additional clients and use its feature to directly "attach" USB devices to a virtual machine. That way additional keyboards/mice can be separated (hint: It's easier to distinguish different keyboard/mouse brands to associate the correct device with the respective VM), and if your sound card has e.g. separable front and rear exits you can even split sound.