"(like reverting files back to all default etc)"
And which files (or type-of files) would these be?
The way I work Bill is I keep backups of all the original main folders (texture, sound, gauges, effects etc). I then add files to the sim as I want to (eg new effects go into the effects folder as usual) but in case a 'dirty' file gets in there, I have always got the originals to revert to with out having to get em off the CD/DVD. It also means, as here, you can find out very quickly if an error is happening because of something you've added.
Tell you what, it's a great help having separate folders in this version for add on aircraft (flyable and AI) because just by changing the names of 2 folders you can take them all out at the drop of a hat.
Also means that unlike FS9, which loaded up more and more slowly the more planes you added, if you want you can have separate folders for GA, military, choppers, heavies, vintage etc and only load in the folder you want. That could considerably speed loading up.