error 8646

Question

hi

windows login password has been changed automatically and I can not log in to my previous account.

can not change the password for my account now with the admin account, I tested it through cmd and control panel,Computer Management and settings>account, but show :

System error 8646 has occurred.

The system is not authoritative for the specified account and therefore cannot complete the operation. Please retry the operation using the provider associated with this account. If this is an online provider please use the provider's online site.

Answer 1

Hi Peymanh. I'm Greg, an installation specialist and 9 year Windows MVP here to help you.

I'll give you everything possible to try for sign-in failure so that at least something will work:

First see the various troubleshooting steps here:

https://www.groovypost.com/howto/reset-windows-...

https://answers.microsoft.com/en-us/windows/for...

https://www.groovypost.com/howto/recover-lost-w...

This could also be due to account corruption so see the fixes here:

https://www.techbout.com/fix-corrupt-user-profi...

To access another account to try to fix corruption, or create a new Admin account to replace a corrupted account, see these steps to enable the hidden Built-in Administrator used for emergencies like this. First try whichever method works here:

If it blocks these by requiring a password, then first see this tutorial for enabling Built-in Admin from Log-in Screen. https://www.isumsoft.com/it/enable-hidden-admin...

It may also be necessary to create bootable media to access Command Prompt at boot to use Option Five to enable Built-in Administrator, or to Reset or do the Clean install:https://www.tenforums.com/tutorials/2969-enable...

To create Windows 10 Installation Media on another PC install Media Creation Tool and follow the directions here: http://windows.microsoft.com/en-us/windows-10/m.... 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, then Command Prompt to attempt enabling Built-in Administrator.

Restart PC, Sign into new Admin account, elevate the desired account by typing netplwiz in Start Search, opening the wizard, highlight desired account (tick box if necessary first), then under Properties > Group Membership, change to Administrator. Save that and then if desired highlight and remove the old Admin account.

If these fail then create a new Admin Account to sign into and test, move your files over and when ready delete the old account: http://www.howtogeek.com/226540/how-to-create-a...

If that fails go back to Troubleshoot Options to try a Reset.

If that fails 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.

There is a step included to rescue your files first if they are not backed up using the bootable media here: http://answers.microsoft.com/en-us/windows/wiki...

I hope this helps. Feel free to ask back any questions and let us know how it goes. I will keep working with you until it's resolved.

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