|Firstly, are you sure it's a cable modem you have? Cable does not use a standard telephone cable, it has a separate coaxial or optical cable. If your modem plugs into a standard telephone socket then you have ADSL not cable. Also with cable you shouldn't be getting any mention of dial-tone, but ADSL, especially using USB may get a dialtone message.|
If it is definitely cable you have then, as HopperRox says, forget USB as it requires drivers, ethernet will work 'out of the box'. You just need the cable from your cable terminal, plugged into the back of the modem, then an ethernet cable from the modem to your PC, and a power connector to the modem, nothing else.
"I've always been mad, I know I've been mad, like the most of us..." Pink Floyd