Hi Alan. I'm Greg, 10 years awarded Windows MVP, specializing in Installation, Performance, Troubleshooting and Activation, here to help you.
If you cannot change your password because the Security info stored here was not kept up to date: https://support.microsoft.com/en-us/help/12428/... or password or password change is not working properly, then you'll need to do Account Recovery.
If you can prove it's your account by knowing enough information about it then they should let you recover it, possibly after a waiting period during which they observe the account to see who shows up. Otherwise they will not budge because after decades they have this down to a science to be sure they're giving your information only to you and not a hacker or stalker.
So spend as much time as necessary in this walk through of the Account Recovery form to prove it's your account which is what matters most:
https://support.microsoft.com/en-us/help/17875/...
Meanwhile if you're locked out of Windows I will show you how to create a new Account so you can still get into your Windows install for now using all of it's apps and accessing data, or if necessary reset or reinstall Windows.
Create the new Local Admin account directly from the Command Prompt as shown here: https://www.isumsoft.com/windows-10/3-ways-to-c...
This requires accessing the Command Prompt using bootable media which is the only method that doesn't require a password. If you don't want to do that then you can try now to Reset Windows 10 from the Sign in Screen as shown in this video:
https://www.youtube.com/watch?v=Zonjyd2L_GQ
To create a new Admin Local account go to another PC to create bootable media following the steps toward the bottom of the download page here in the section "Using the tool to create installation media:"
https://www.microsoft.com/en-US/software-downlo... Uncheck the box for Recommended Settings to choose the exact version and bit rate for the target PC only.
Insert media, boot it by powering up PC while pressing the BIOS Boot Menu Key: https://www.sysnative.com/forums/hardware-tutor...
If the media won't boot you may need to enter BIOS/UEFI Setup (pressing key given in chart in link above) to turn off Fast Boot or Fast Startup first.
Choose the boot device as a UEFI device if offered, on second screen choose Repair Your Computer, then Advanced Troubleshoot Options to open Command Prompt create a new Local Admin account to replace yours:
https://www.isumsoft.com/windows-10/3-ways-to-c...
Sign into the new account, set it up, check all apps work or reinstall any that don't, access your files via C:\Users. It will give ownership with a green progress bar that travels across the URL box until all files are unlocked and available.
If that fails you can go back into the bootable media to Troubleshoot Options to do a Reset saving files. You can also rescue files beforehand using the same bootable media via one of these methods:
http://answers.microsoft.com/en-us/windows/wiki... and then do the deeper clean reset since you have to reinstal your apps anyway and it's a cleaner install.
And if all that fails from bootable media choose Install Now, then Custom Install, then at the drive selection screen delete all partitions down to Unallocated Space to get it cleanest, click Next to let it create needed partitions and start install - this makes it foolproof.
Everything needed to get the best possible Clean Install is here: http://answers.microsoft.com/en-us/windows/wiki.... It is a better install than any amount of money can buy and a great learning experience that will make you the master of your PC because you will learn what works best and how to apply it with your own hands.
I hope this helps. Feel free to ask back any questions and keep me posted. If you will wait to choose if I solved your problem, I will keep working with you until it's resolved.
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