I think there is a solution. You should change the connectors of the cable (crossover cable) and try connecting the computers without switch. Next, you have to buy another NIC Network Card and plug it on the PC where is the ADSL Modem is installed. And then that PC will have 2 NIC and just Bridge the connections and the second PC will have access to the ADSL Line.
I think you will find that using a crossover cable will not work. If one port is bad just add another small switch using the good port. I think you proably have a router not a switch, unless the ISP gave you multiple IP address. If your adsl has multiple net ports you could connect direcly to the modem.
You could share the internet access through one computer if you have multiple nic cards. The down side would require one computer to be on before the other could connect.