Thanks Fugitive. I was under the impression that Steam used a "streaming" methodology rather than running directly from my hard drive. There is no doubt that when I run Flight simulator 10 directly from my hard drive It freezes after about 10 - 15 minutes of play, whereas played through steam a get over half and hour, before any sign of instability. That's what lead me to believe that it was streamed so I can't explain the difference.Also when I ran steam for the first time it asked if I wanted to transfer my original setting, I didn't. When I ran steam version I didn't get any of my joystick buttons to operate.
I think I will run the steam version (at least for a while) and see if there are any differences.
Matelot