riser

Illustrious
Set all the computers to have the same Workgroup and use a switch. Enable file sharing if you need to access files from each PC.

Default, your workgroup might be: MSHOME.

Set it to anything you want, may require restart, and you should see any other PC using a switch/hub that has the same IP address. Add in DHCP via a router and they should all be fine and using the same internet connection over the router.