1. Connect the computers in LAN with the switch and cable you have.
2. Connect the broadband connection to a computer (the one you want to make server).
3. You can do well with windows connection sharing.........but i recommend to use CCProxy(the free version supports maximum 3 users) or freeProxy.
4. Install it on the system u want to make server.
5. Configure the IP of all the 3 systems to the same series and make them member of the same workgroup.
6.Create accounts in CCProxy for the other 2 computers.
7. In those 2 computers go and set the proxy in ur browser and other progs as the ip of the server.
CCProxy works on 808 port no. for all protocols except for SOCKS where the port is 1080
FreeProxy works on 8080 port.
Try yourself....I think its not that tough.......
If you dont want 2 use ne program like CCProxy then go to your internet connection properties and there go to sharing tab and share with ur lan connection.
Then u can access the net in all three computers.