Does Time Machine delete the most recent backup used when migrating files after using Setup Assistant? The reason I ask is because I think I messed up when I migrated all my files over and I'd like to start over., but don't know if my last backup still exists. Also, when I migrated from Lion to Mountain Lion some of my desktop wallpapers were missing. Does this mean I've lost some of my more recent files? Thanks for any replies to my dumb little question.