Hi Jean, It sounds very much like you have Time Machine enabled, but have for whatever reason not been backing up to your selected Time Machine disk.
If you no longer wish to use Time Machine, turn it off in System Preferences to reclaim your backups storage. Or, if you wish to use it, back up at least once to a storage device, and you should flush your 40 GB of backup history to your storage device and free up that space on your main disk. It’s also possible to leave Time Machine on, but turn off the local snapshots feature, thus allowing you to back up whenever you please without consuming backup space while you are not connected to your backup disk. I don’t recommend you do this on a mobile computer, though, because the feature is useful while you are away from your storage device. If you want to do it, there’s a Terminal command. Cheers, Sabahattin -- You received this message because you are subscribed to the Google Groups "MacVisionaries" group. To unsubscribe from this group and stop receiving emails from it, send an email to macvisionaries+unsubscr...@googlegroups.com. To post to this group, send email to macvisionaries@googlegroups.com. Visit this group at http://groups.google.com/group/macvisionaries. For more options, visit https://groups.google.com/d/optout.