I would like to backup the right files to that every time I change my laptop I do not have to click authorize computer.

I have already used 4 of my 5 possible.
So what files need to be backed up. If you could give me a directory and file name.

Also is the latest version of 9.x itunes safe for hacked / cracked phones.

You can always de-authorize all previous computers and start again if you get to 5. I think this file uses a key based on something unique from the machine's hardware so simply backing up a file will not work.

You can also de-authorize all 5 computers once in a year, in case you run out of authorizations. I had to do this a couple months ago, when I replaced my home machine and a major incompatibility issue surrounded me, taking away all my 5 auths.

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well my laptop crashed.
Being a good boy I have taken regular backups.
So how do I de-authorize an account if the laptop has crashed.