How do I unlock Library Extra.itl?

Have you applied the main advice in Repair security permissions for iTunes for Windows?

Have you tried temporarily disabling your anti-virus software? What is it by the way?

Right-click the iTunes shortcut and use Run as administrator to see if that helps.

See Open a different iTunes Library file or create a new one - Apple Support and see if you can create a new test library.

tt2

iTunes Library Extras.itdb is a private support file accessed by your main iTunes Library.itl file. Likewise iTunes Library Genius.itdb. If either file is missing they can be recreated as required using data in the .itl file. They are not intended to be opened directly by the user. What are the circumstances that led to the question?

See Repair security permissions for iTunes for Windows for details on setting the correct security permissions for file in the iTunes library folder.

tt2

I've just added this section to my user tip on permissions which I hope covers your situation.

File is locked, on a locked disk, or you don't have write permission errors

In some cases Windows Defender in Windows 10 may block file activity by iTunes that should be allowed. See how to turn off Controlled folder access in Windows Defender Security Center in order to allow iTunes to run normally. Other anti-virus software can potentially cause similar problems, and excluding the iTunes folder from real-time scanning may help.

tt2

I consider turingtest2 the guru on these matters. I would follow his advice in the Removing and reinstalling iTunes and other software components section of:

Troubleshooting issues with iTunes for Windows updates

You're most welcome. 🙂

Would you mind sharing which bit of advice finally did the trick? Might help me prioritise suggestions in future.

tt2

Cool. Have been able to add all of your media to the new library? Is there any lost information such as ratings and playlists that you'd want to recover if possible?

tt2