If u have lan card,try the command in terminal(Applications>Accessories>Terminal or right click anywhere on Desktop and open terminal):
press enter and give ur passwd.enter again
now u need to answer few questions.answer carefully.first username,password,then do u want connection starting automatically at boot time or not etc..
Now u can have internet.for internet switch off use "poff dsl-provider" command.for on, "pon dsl-provider"
Now with internet connection "on"..try this:
in menu System>Administration>Synaptic Package Manager this will open a nice gui package manager which shows the installed and installable packages.
just search in synaptic(CTRL+F) nvidia and see the results.the packages @kalpik said also will be there.double click to install those packages.thats it.
I think u uses @freebirds /etc/apt/sources.list.it's fine.