I'm a new Mac user... so I don't know if i'm doing something wrong or what's going on.. I plugged in my hard drive which had files backed from my previous computer system.. I wanted to put some of them ( such as music) onto my Mac... & I'm able to copy anything from it but when i try to right click and delete.. the option is not there or when i try to move any file to the trash.. the errors reads: " Can't delete the file as it cannot be deleted" What should I do???