Answer:
What word becomes shorter when you add two letters to it?
I make billions of dollars selling Windows. Who am I?
What comes down but never back goes up?
A man goes out in heavy rain with nothing to protect him from it. His hair doesn't get wet. How does he do that?
Old Mcdonald had this
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.