How to solve iOS backup issues in iTunes

Error message: iTunes could not back up iPod because the backup could not be saved on the computer

A few days ago, I was helping my daughter update her Ipod Touch to a newer version of the iOS software from the one she had installed. Every time I tried to do it, iTunes would download, unpack, verify the download, start the installation, try to backup only to fail. The error message was: “iTunes [...]