Don't forget that, as  well as the files that BeechPapa listed (good to know), if you have other complex add-ons such as PMDG stuff, there may be other files installed and/or registry changes that may not be captured by those file locations.  I would say to back up all of C: (assuming your OS is on C:) plus any other drive that you have your FSX root on.

 

Good thread, Bruce.

 

Not necessary to pay a dime for quality disk imaging software.

 

DriveImage XML does a great job for free and also supports restoration of just individual files/folders if desired.

 

It has saved my bacon several times.

 

www.runtime.org/driveimage-xml.htm

 

John