What is the best way to respond to this obvious scam letter?

[http://i.imgur.com/v0opa.jpg]

My girlfriend received this letter today... it made us laugh for a few minutes** but It's scary how many people fall for this type of stuff.**

I would like to troll them/waste their time and thought it would be fun to respond and see what they try to do.

If/when they reply then the fun begins...

What are your suggestions on how to do it/what to write?