Lenny - There are 5 classes in Diablo II -

Amazon
Barbarian
Sorceress
Necromancer
Paladin

When LoD came out, they added two more -

Druid
Assassin

(which weren't very successful)

To everyone else - Give the kid a break, damn. It was an honest question (as the title even states) and there's no reason to make fun of him for not knowing. I'm not trying to be some Supreme Moderator and scold you all, I just think what you've been saying is not really necassary. (Excluding Lenny )

Hope that clears everything up!