It is hard to troublshoot this issue unless more information is provided. What windows operating system are you using? It sounds like both computers maybe given the same IP address causing conflicts. Are you sure it is a router that you are using to connect both computers to your DSL modem? A hub, switch and router are three different units. If it is a router there should be a reset switch or a tiny hole that you stick a pin through to reset the router. I would power down your dsl modem, and router for about 20 seconds. Then power on the dsl modem, then power on your router.
