I have used a USB drive connected to my iMac for several years to store my time machine backup. My wife is switching from an old windows computer to a new MacBook Air, and I plan to backup her new MacBook to the same drive. I have connected the drive to our Airport Extreme, and partitioned it so that there is a dedicated space for her backups. Everything is working properly, however I would like to remove some old files from my backup so that I can allocate more space for her backups. My backup takes up 2.5 TB, largely because of movies I have ripped and stored in my iTunes collection. To free up space, I went into Time Machine and chose the option to delete all backups of the iTunes movies folder, and also to exclude that folder from future backups. After entering my credentials and verifying the folder had been removed, I checked to see if there was any more free space available. Excluding this folder only freed up a roughly 25 GB of space. I was expecting 1 TB or more. My question is do I need to empty the Time Machine trash (if that exists) or perform some similar operation to reclaim this space?