If you look carefully at the ports, you might see one that is slightly smaller than the others, i.e. it has an RJ11 (telephone) socket, whereas the others are the slightly larger RJ45 (network) sockets. If so, this has a modem, and you connect the telephone cable to this, instead of to your modem.
You then need a standard (not cross-over) Ethernet cable to connect between the router and your PC's network card.
You really don't have to buy a new router. Throw away your ASDL USB modem (not literally) and connect your phone line to your present router, as jazzypop says. You don't need to use a router and a modem. Reading the details that ßéŁâ posted, you can in the future, add more computers if you wish as it has an integrated 4-port switch.
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