h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

OMG is it just me, or has any other women out there experienced guys mocking them when it comes to computer/consol games??? at school, there is a Halo 2 tournament, and ive played. for my second attempt at the game, i was told that i did pretty well. but still, guys who dont even know me mock me because they think girls generally are crap at games. i quite a gamey person, and i pick things up easily, so why is there so much sexism??? is it because guys think girls are incompetant, or is it because they cant admit that girls are good at games??? please enlighen me, i really would love to get to the bottom of this whole fiasco!