I have a 1TB Mac HD and a 1TB Time Machine external drive. I have only used 850GB on my Mac HD, so according to math and logic, I should be able to fit this 850GB on the 1000GB external Time Machine drive... but according to Time Machine logic, there isnt enough room. It keeps telling me it needs so and so many GB to back it up and that it hasn't been backed up for 20 days. I understand that it is backing up old files that I do not need anymore or have purposefully deleted, but I would just prefer it to make a backup of what I have on my computer At the Moment. Is there a way to turn off Time Machine's extra "feature" of clogging up the drive with old unwanted files instead of backing up important current ones?