As a personal preference I never use Autogen and neither am I interested in Missions or Lessons. Can I remove them from FSX without any problems being caused? No plans to remove them but just want to know if I could if I wanted to. Anything that reduces file sizes reducing search time and defrag time is the angle I am seeking.regardsjc

Personally I would never remove any default files. There could be unknown interactions between files that could be disrupted if any are removed.

Keeping in mind the previous poster suggestion, you could make anew folder named "Unused Default Files". Place whatever filesyou're considering removing into that folder and see what happens?This way if there are problems just put the files back in their original location.But, I would never just plain delete any files!Also, any benefit to this procedure is going to be very, verysmall, so why bother?

never remove anything from a program installation.It can only lead to tears.The microscopic and theoretical performance gains you're after are not worth it.