.s1 is right. Go into your network adapters properties, select TCP/IP, and set everything to automatically get...
Next, shut down your computer, and unplug your modem. Plug your computer directly into the modem, and power the modem back up, makeing sure that the modem has been down for at least 10 seconds. Turn on your computer and it should work.
The reason that you have to power cycle the modem is each network device has a unique MAC (media access control) address. When the modem initializes, it will only communicate with the MAC address of the device it found when it started up. Since your router and NIC have different addresses, you have to power cycle to make the modem communicate with your NIC instead of your router.
Good luck.