Ok a simple question. Firstly I have a Flight Simulator X which by far is the Biggest Program ever made (15 or 16GB). I have a Compaq Windows XP that only as 64 GB of hard Drive.

I can't play the Game without it lagging or freezing, and I've heard that it plays much better on a Vista or any Computer System that is far Advance than the XP Windows. Can somebody tell me
What between XP, Vista or Other which one is Best Recommended for The Flight Simulator X? If I need some device or some kind of Equipment please let me know so I will know what to do in order to play my Flight Simulator X again.