Ladder Theory.......read it
http://www.intellectualwhores.com/masterladder.html
a little quote....
"Many women want to argue this point and say things like " I have lots of guy friends." Maybe. There are exactly 3 cases Intellectual Whores has identified whereby a guy and a girl can be friends:
The guy is gay
The guy does not find you attractive.
The guy already has a woman much higher than you on the ladder."