A geek is somebody who is completely upset with something.
Wait a minute... isn't that an Emo person?
As far as I know, Geeks and Nerds are pretty similar, except that Geeks are known for having cravings for polyester clothes with bowties and orthopedic shoes, science fiction and regular old science for that matter, and those role-playing boardgames. Not to mention that they can be really smart.
Nerds on the other hand, tend to wear things like needle-point sweaters with button-down shirts underneath, but aren't necessarily obsessed with science, they seem to like computers more and things like comic books and video games. And they too can be really smart.
So for that matter, I am a Nerd, I am NOT a Geek.