Hey Buzz sounds like you've managed to screw and corrupt the Registry keys for FSX if you've been going through and doing lots of uninstalling and re-installing of FSX. That's if you have previously had a Boxed CD version installed on either the same or a different drive.
Recommend doing an uninstall 1st then go through and do a registry clean up then
Restart your PC before either a fresh clean install or re-install.
You will need download and get a freeware Registry Cleaner, you can take your pick and choose from various Flight Sim websites
Such as TweakFS
http://www.tweakfs.com/store/free_tools.phpDownload the file FSX Registry Utility for the fsx_reg_utility.zip
Use this link for a guide
http://fsrijnmond.airworld.nl/FSX%20Ste ... FSX-SE.pdfOr you could try Flight1 freeware FSX/FS9 Registry Repair Tool
http://www.flight1.com/view.asp?page=libraryInstall or run these as the administrator of your PC to fully clean up the specific FSX Registry setting keys.
Then you should be able to do a fresh clean install of the Steam FSX SE
If you're going to install FSX SE then check after the uninstalling FSX the Boxed CD version and make sure in your Windows Explorer that their is no C: Program Files (x86)\Microsoft Games\FSX
My FSX SE is now install on a separate a 1TB SSD, I went through several uninstall and re-installs after having the previous CD Boxed version installed on the C: I managed through trial and error and got it sorted in the end.
Drive Path should look something like F: Steam\Steamapps\common\FSX
You may also need to check the C:\Users\Your name\Appdata\local
Check that their is no FSX directory here it may be left over after doing an uninstall of the boxed version of FSX.
The Appdata folder is a hidden folder so you will need to unhide the subdirectory folders underneath to be able to see and delete the FSX folder of the boxed version if it's still showing up. The Registry may be still pointing to this invalid directory if it's not cleaned up after doing the uninstall.
Any installers for re-installing Addon Scenery or Aircraft Sim Objects will need to be manually changed with a typed entry to point toward the new Drive Letter pathname installation eg F:\Steam\Steamapps\common\FSX