iTunes won't open after update My iTunes will not open under my username after an update.  It pops up an error message saying "iTunes will not open. An unknown error has occurred (13001)".  However, I tried troubleshooting it from the Apple website and got no where except I know it works under a different user.

Can I fix my iTunes without having to delete it?
Reading this thread and this article, it seems as if your library is corrupt.  

Follow the recommendations and instructions from the above linked official support article for error 13001.