So, the core of iTunes's being is in the "iTunes database file" type file, which is given the default name "iTunes Library" with no extension. Mine is 6 MB. You should be able to open iTunes using one particular library file by holding down Option when you click iTunes's icon, and then clicking "Choose Library", and then browsing to the file. The file should have black text and be clickable. My "iTunes Library" file is displayed in gray text and is not clickable. However, it is byte-for-byte identical to another copy of itself which is clickable. The filename is identical, they are in different directories with the same exact permissions. Currently, when I do "Get info" on the functional "iTunes Library" file, it says General > Kind: iTunes database file. When I do "Get info" on the non-functional "iTunes Library" file, it says General > Kind: Document. How can I change "Document" into "iTunes database file"? It IS an iTunes database file. It is byte-for-byte identical to the working version, I compared them two ways.