Windows XP Remote Connection to a computer not on my network?

My mom is the most computer illiterate person in the world and it pains me to walk her through things step by step. Even saving pictures from a hotmail email is difficult to explain to her. How can I setup remote desktop so I can control her computer from my home while explaining to her what i am doing?

both computers are running windows xp sp2

Never mind figured out how to do it via windows messenger. I was confused with remote desktop and remote assistance.