you could do either of these:
1) Wired solution:
Leave the modem where it is and hook up a long ethernet cable from the modem to your network card on your PC in the other room.
you can buy ethernet cable from
HERE and they are cheap to buy.
2) Wireless solution:
Leave modem where it is and hook it up to a wireless router.
Put a wirelesss PCI card in your PC, install any drivers that came with it.
Then search for the wireless network.
Remember to set up security in the Router's setup page.
There are some reccomended Wireless routers
HERE