Change settings on Home Network

I have a home network with 1-desktop, 2-laptops and 2-printers connected via
D Link router using DSL for internet access.

When I originally set it up I allow each workstation to access the internet
independently or as stand alone. Now I want to change that where the desktop
will be dependent on my laptop to access the net. How do I make the changes.

Also, how do I set up a peer to peer network (intranet) within my LAN with
the interenet access disabled.

Your help on this will be very much appreciated.

Thanks,

Mike