I assume that you had a Mac previous to purchasing this MBP.
If this is correct, did you use the Migration Assistant to move your stuff from the old machine to the new machine, including accounts and settings?
This would have solved all your current problems.
Try this. Remove the iTunes library that is on the MBP by dragging the entire iTunes folder from your music folder onto the desktop.
Connect the external drive
Fire up iTunes and it "should" ask where the library is. Point it at the external library.
Check to see if you have the same problem as before.
If you don't, come back and we'll work on moving the library onto the MBP.
P
MBP 2.4 ghz running 10.6.4
iTunes 9.2.1 (4)
Factory refurbished model that I have been using now for about 10 days.
OK, so I got a new macbook pro. Now, I had been keeping my iTunes library on an external HD but I decided to migrate the library over to the new computers HD by hooking up the external, and using the Add To Library to import all my tunes. I have never purchased any music from the iTunes store, but I did have some free downloads from them.
I went to get a free compilation from the iTunes store last night, and got this message...
iTunes couldn't download your purchase
You don't have write access for your iTunes media folder or a folder within it. Change permissions (in the Finder) and then chose Store > Check for available downloads
Well, I did all this, made the permissions both Read and Write in all the folders associated with the iTunes library... and still no luck. I reset the path to the library in the iTune preferences panel >advanced settings, and still no luck.
I then decided to reauthorize the account, but got this message when I entered my iTunes password...
There was an error storing your authorizations information on this computer.
The required file was not found or has a permission error. Correct this permissions problem and try again, or de authorize this computer if the permissions cannot be changed.
Now, I have found tonnes of info about this (or similar) problems on the net, but no one seems to have posted a consistent fix. Proposed solutions vary from fixing the folder permissions in the Finder (which I have done 3 or 4 times now), to messing with the media library xml file, to dragging the whole library to the desk, restarting iTunes, then importing the original library back to the rebuilt iTunes folder. I imagine that if this is a DRM issue (which I suspect it is) then that last solution won't fix the problem either.
Will doing an Archive and Reinstall solve the issue? Can I just throw away all of the DRM tainted items and regain access to my iTunes library? How would I even identify which songs are even using DRM coding?
I'm considering doing an Archive and Reinstall anyway, because this computer is acting a bit buggy. I'm not sure if this could be a hardware issue since this was a refurb model, but I haven't done all the hardware test from the OS disc yet, since I've been busy reinstalling software and libraries from my old computer.
Thanks folks, for any help you can give me on this.

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