The Windows 10 login password went amiss for Albert Pye and about a dozen others who wrote to me saying they couldn't log into their PCs. In every instance they had not touched their computer nor changed anything, yet all of a sudden their password or PIN was incorrect.
Microsoft hasn’t acknowledged it specifically in its update log, so that makes me think it’s a strange brew of circumstance and hardware/software malfunction, perhaps some problem with the installation of an update. These workarounds could help you.
First, try using the on-screen keyboard to enter your password or PIN, as I’ve read that could work when your regular input devices don't. Click the Ease of Access icon (it looks like a sort of clock with a dotted circle) in the lower right-hand corner of the screen.
If that doesn’t work, one reader successfully “fixed” this problem by using Windows System Restore to go back in time to when the previous password or PIN worked.
Because you can’t log into Windows, you’ll need to access System Restore via a recovery disk. This simple process can be done on any Windows 10 computer and used with any other Windows 10 computer of the same flavor (32-bit or 64-bit). The easiest way to find this feature is to type create a recovery drive into the search bar in the taskbar.
Note you’ll need to sacrifice the contents of a USB key ranging in size between 8GB and 16GB. Also if you experience trouble with this process, read this article for helpful suggestions on how to fix it.
If you don’t have a recovery drive, you could download the Windows 10 installation files. Once you’ve created a bootable Windows 10 installation disk, boot from it and then press Next at the first screen you see (after you select your language). The next screen asks whether you want to Install Windows, or Repair your computer. Select the latter.
On the next screen select Troubleshoot, then you'll have access to two handy tools; System Restore and Go back to previous build on the next page. Since you might not be certain which update hosed things I recommend using System Restore just to be safe. Click on it, then select your OS, and you’ll have access to System Restore.
Follow the prompts to select an earlier time to restore your PC. If you’ve found another workaround for this issue, please let me know in the comments.