Moving Library Fileand album art only

Never tried this before, but it should p'bly work (and it risks nothing)...

With iTunes quit, copy the "iTunes Library.itl" file and the artwork folder to the external. Ideally, they will go in a folder that contains the folder that holds all your music folders (as in the "iTunes" folder which contains the library file, the artwork folder, and the "iTunes Music" folder that holds all music files), but I imagine it can go most anywhere...

Then, fire up iTunes with the Shift key held down; iTunes will prompt you for a new or existing Library file; locate the iTunes Library.itl file on the external. Everything should be good at that point. If not, just quit iTunes and fire it up again with the Shift key down and select the library file on the C: drive -- no harm, no foul ;-)

Of course, to use the external's library on another computer running iTunes, you'll have to do the start-iTunes-with-Shift-key-down thing to get your library recognized (and do it again to reset to normal library when done, if courtesy plays a role in this ;-).

One possible problem is the drive letter...dunno if this will work on a machine where your external gets recognized as a different drive letter than on your machine. When the library file is in a folder named "iTunes" on an external (and the music files are inside the iTunes folder) there's usually no problem (maybe iTunes tries relative paths from the Library file...I dunno); not sure what happens in other conditions. P'bly best to field-test on another computer before declaring success...