I believe you are confusing dial up with pppoe. Though you have to "dial in" to the server and authenicate before you get on the internet, you are on a broadband connection.
I suspect you need to clone the mac address of the single working pc to that of the routers wan interface. This is very simple to do. Usually there is in the wan config page a button to "clone workstation mac address" or a place to input the mac address of the pc that can get online.
You can get the pcs mac address [physical address] with an ipconfig /all at a cmd prompt.
Your router also needs to support pppoe and you need to set it up with the pppoe password. This should all be covered in the router user manual.