Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
I had a very similar problem but stuck at 90% for 2 days, went through the procedure as above '' right-clicking on the drive in My Computer, going to properties, security, advanced, owner, and take ownership. I set the owner for all files to "Administrators". It was previously set to ''trusted Installer''. After this I rebooted, when my lap top restarted it asked one more question relating to office 365 installation and then all ok!!. 90% message now gone and as far as I know all working ok. Thanks to JW for the info.