Why do all the windows in my house have condensation?

This is something we all struggle with, even the high end homes can experience this. Invest in new, High energy efficient windows is a bonus, if you swing it. OR a minor inconvenience.
Please read.
http://answers.yahoo.com/question/index?qid=20080119082912AA1mKXhWhy do all my windows have condensation?....Winter aggghhhh!