I really have to say, you are trying to reinstall a game from a corrupted CD
And you wonder why you get the msg?
Note that a post on another site said there were uninstall problems with FSX. This is because FSX uses a install package that has a MSI file in it. When you run the installer, it unpacks the files TO A TEMPORARY FOLDER AND DELETES IT WHEN DONE.
Problem,
the uninstaller needs the original MSI file on your hard drive, duh, it's not there. Uninstaller fails. There are other games/apps that have the exact same problem, NERO for example.
NERO provides a special tool to fully uninstall their software, which means they are aware of the problem. You MAY need something similar from FSX Tech Support.