That's an old "early and still in production" version of it and I don't think it's actually still available (Although I do have a copy if anyone wants me to send it to them).
The new version, you have to pay for, but it WAY less buggy, a lot more realistic, and has a lot more enhanced graphics (My system can't handle it). They have a demo on site.
You can see the current version here:
http://www.space-shuttle-mission.com/
It's the most realistic space shuttle simulator that you can get for the PC.