If I re-install FS-9 over my existing installation, will I have to re-install all add-ons including aircraft?

If you're doing the reinstall because you have some kind of problem(I'm guessing this is the reason) with the present install - installing over the old may not cure it (depending what the problem may be).In order to get a "clean Install" but preserve your aircraft,gauges,effects,addon scenery etc - do this...........Rename the existing FS9 (EG oldFS9).You can if you wish do the same with the FS9 config folder in the Docs and settings.(doubtful benefits of this)Install a new copy of FS9.Then open up both old and new copies - copy the Aircraft,Gauges etc etc from the old top the new allowing overwrites.Any addon scenery should be added to the Scenery library once again after the copy across..One you have copied all you want then you can delete "oldFS9"

Every time that I've had to reinstall, the install executable would not permit me to install over an existing installation. It makes you un-install first and then install.BobL