probably need more info on your issue. First thing that comes to mind is a driver issue. Does Ubu recognize the modem/NIC?

How do you go on the internet? Do you have a router? Do you have a wireless network? Does your internet provider allows connection with linux? Do you use ADSL? Does Unbutu recognize your hardware? Are there some known issues with the drivers? Which version of Unbutu do you have? Could you please give the exact text of an error message that you get? Where do you have a problem when using such a basic procedure (example for Unbutu 7.04): "Basic Procedure This section describes the basic procedure for connecting to the Internet. If you have a wireless connection or connect to the Internet through a modem (including an ADSL modem), and this section does not work, you should read the section called “Wireless Cards” or the section called “ADSL Connections”. To connect to the Internet: Open System → Administration → Networking. Select the connection you wish to use, then click Properties. Ensure Enable this connection is turned on. If your ISP or network administrator has given you an IP address, set Configuration to Static IP address, then enter the address in the IP address field and click OK. Otherwise, set Configuration to DHCP and click OK. To activate or deactivate network connections, select your connection, then click Activate/Deactivate." Source and further information: https://help.ubuntu.com/7.04/internet/C/connect-to-internet.html

Ok, it works now. Thank you, except now the only problem is the sound. Its very choppy, and sometimes it doesn't play at all.