My macbook is now four years old and the last wipe is a while ago. My hard drive is quite ful and I don't really know what I can delete and what not. There's also 26 GB in Movies which don't appear nowhere. I really would like to get rid of them but don' know how. So, is there an application like CleanMyMac that is of any use or how can I wipe the hard drive myself (after I saved all my data)?