Microsoft Flight doesn't require any disks and, as I learned today from Jen Deyenberg, it can be downloaded for free. Check out the promo video below.
Microsoft Flight is what we call a freemium game. The basic game is free to download and play, but there are some upgrades that you can purchase from the Microsoft Marketplace.
Applications for Education
I downloaded Microsoft Flight but haven't played with it for more than ten minutes yet, but my initial thought is that it might be a fun way for some students to experiment with some basic aerospace physics. On a related note, Google Earth has a flight simulator which you can activate by going to the tools menu and selecting "activate flight simulator" or by press "ctrl+alt+a.