Disappearing Gearwheel!

[lisapeng]

If you cannot get an earlier save to work, upload a save file and I should be able to edit it so that the game thinks you have solved the machine room puzzle, so that you can start the elevator. Please make sure you have solved the rest of the machine room puzzles so that you don't miss out on anything.

How can I understand "get an earlier save to work"? Is there any way to kind of "back up" to the previous save?
And it'd be awesome if you could do this!
where do I find my savefile?