Recently as I was working on a friend’s laptop (Toshiba Satellite) and was restoring back to the factory defaults and thought I was stuck in a loop, I wasn’t.
They system kept rebooting and saying, “Preparing your computer for first use”. Then it would boot into a Toshiba system customization in progress screen, this image:
This screen does not show you what is happening in the background, installing stuff and configuring. It seemed to be in a loop as there was no progress bar indicating what was being done. It wasn’t until I moved this screen away did I see different icons on the desktop.
Just let the configuration keep doing it’s thing, rebooting and it will be done. It took about maybe 15 restarts for mine to be done.
Hope this saves someone some time down the road.