How do I change my age on Xbox Live or Hotmail?

I'm 17 and I need to change my age on Xbox Live to download content. I've heard you can do this by changing your Hotmail age. Can someone tell me how to do this with much details plz.How do I change my age on Xbox Live or Hotmail?You can't change your age on your Live account, sorry :( You'll have to register another one to do that.