Spud,
If you can't get your DVDs to reinstall FSX, try a system restore to the point that you had it installed into the default so called "no, no" location. Lot;s of people have no trouble running it from there. It was just recommended to install elsewhere because people were fighting permission issues. Also, if you have access to another computer with a DVD drive, see if that drive reads the disks. I've had instances of my drive not liking certain DVDs or CD, but a drive in one of my other computers has no problem with them. This will at least tell you if you have faulty disks or not. If they read fine elsewhere, post back and I can help you get them installed on your main system with a little trickery.