I have three Lenovo laptops running Windows 10. Two of them recently had a problem (I'm assuming during a Windows update, though I wasn't awake for that). All of a sudden the screen reverted to the Windows boot-up spinning circles, then hung up there. When I turned the computers off manually I got a message that Windows was attempting to return to a previous version. On one of the computers that eventually seemed to have worked. On the other (older) laptop, it worked for a while, but when I woke up this morning it was back to the spinning circles and I can't get the system to boot. On the computer that didn't seem to have this problem (it successfully went through what appeared to be a major Windows update), several of my add-ons were disabled (e.g. some of Norton, PDF, Intel anti-theft, and others). My main concern is the computer that doesn't work at all - I would think that Windows would check for appropriate system resources before imposing an incompatible update. The laptop is only about five years old. Please help.