Help on Ethernet driver

OK, I am a self-proclaimed computer illiterate person.  I have a 6-year old computer (Dimension 2400).  It still works fine so I have had no reason to get a new one...however, I have recently taken the big jump (for me) from dial-up to RoadRunner.  My problem is that I no longer have the CDs that came with my computer so I can't install the ethernet driver that way.  I went to the Dell site to download it...and OMG!!...there's so many!  I don't know which of the 10 to choose...or do I need a ethernet controller driver?  If someone can please help me so I can get on line without having to go to the library to use the computer I would be forever in your debt.