Why is my secondary hard drive acting all weird ?

Have you tried booting first then plugging in the drive instead of booting with it connected? Hopefully you can do that and still read the drive. If not...I hope you have those 13k songs backed up somewhere. A hard drive, in an enclosure or not, isnt designed to take a beating (unless you buy a toughbook lol, those are designed to take a hit) Sorry I couldnt be of any more istance. Best of luck! If you do end up losing everything on it and do not have a backup, I would strongly suggest making a regular backup of the contents of the drive, especially if your job depends on it!