I would like to operate a DSL computer about 400 feet away from the modem. What is the likelyhood of success??
Make two segrments. Plug a long ethernet cable into the dls router and then into a small ethernet switch, plug one more cable into the switch and run it to your machine.
PS, try to make the two ethernet cable lengths about half the total distance so that the signal on the line doesn't suffer attenuation, and make sure it isn't directly near any power supplies or lamp balasts.