So I have been backing up my macbooks' internal HD for a while now with the Time Machine automatically backing up with the setting ON in the system prefs pane. Recently I turned automatic updates to OFF because I didn't want it to back up every time I connected my time machine disk to my computer. Keep in mind the old backups take around 4GB of space because Time Machine only adds the new files. Now after a few weeks, I want to back up again, so I click "back up now" on my time machine disk and it wants to update it w/ 93GB of stuff which is taking FOREVER. If you have any idea on how to fix this (not completely back up the OS again), it would be greatly appreciated.