I'm no sure of the difference between geek or nerd, my Interpretation has always been:
NERD; into sci-fi, roleplaying, statistics, continuity.
GEEK; into all of the above plus likes to know everything about gadgets(techie).
I've never been too ashamed by liking star trek, before TNG, when I was a young man, we used to host 'landing parties' and a lot of non-scifi folk would turn up in some wierd home-made fancy dress alien/starfleet outfits. Happy days