FSX and FSX Steam edition compatabilty

I have been having a hard time getting my FSX or my FSX-SE to play well together. Steam edition will not load several of my favorite airplanes, so I reinstalled FSX on a different drive. I now receive the following message when trying to open FSX (original):

Unable to cache file: "C:\ProgramData\Microsoft\FSX\SceneryIndexes\FileList (with a bunch of FileList numbers) You Must Lof on as a user with write permission. Destination drive may be full or set to read-only, or a file with the same name may already exist." Click abort to exit.

Now I'm thinking perhaps if I uninstalled Steam it might work, but I thought I might check here first, as my computer expertise leads only to frustration and a trip to the repair shop.

Anybody?

The following fsrijnmond install guide for FSX and FSX Steam may be helpful. It will show you all the paths. It explains the dual install setup as well.

http://fsrijnmond.airworld.nl/FSX%20Steam%20se/How%20To%20Install%20FSX-Steam%20Edition.pdf