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Last night, what seems to be the same issue, was stopping the PC from booting up. Similar to the explorer issue, Windows started to come in, but then stuck there with a circle cursor rotating forever. Tried to reboot a few times but eventually left it and went to bed. In the morning it was trying to get me to put in a phone number or e-mail address to log into a Microsoft account !!! What the heck was that about ? Had to press a cancel key to get out, whereupon, although it took a while, it eventually came in. But the explorer still freezes with a rotating cursor if one right clicks on a file.