Problem with Internet connection

I just formatted a new partitition and reinstalled windows XP on my Dell Dimension 4550. So my computer is almost like when I received it, the only problem is that internet explorer is not working. It seems that the computer is not recognising the DSL cable (I tried to set up a new connection, but doesn't work).

Anybody have a solution... ??? Is it a driver that need to be installed, if yes what shall I do ?

Thank you very much for your help.