How to edit itunes info on music from my external HD that is read only?

Ok, so i had a crappy old alienware where i managed all my music on itunes thru a fat 500 gb WD external drive, but the alienware is really screwed up, so i moved the drive to my brothers new MAC and successfully got itunes to have the songs load up like on the pc, but some songs arent like i had them nicely organized , so when i try to change the name album or artwork etc it is greyed out or wont let me click on it, so i did a little research and it is because they are read only, which is some security program i take it. i wanna know how to fix this or get the songs to let me edit the info. Also if you think there is a way i can fix it make sure it is safe....i dont wanna lose 8000 songs & 300 vids. thanks any help or info would be great