Hi YJ. I'm Greg, 10 years awarded Windows MVP, specializing in Installation, Performance, Troubleshooting and Activation, here to help you.
TSome times if the User account gets corrupted and cannot start, Windows will sign into a temporary account. A Temp Account cannot be used as a normal account so do not set it up or copy files into it because at any restart it might decide to start into your old Account. I'll give you everything that can be done to repair or replace your account, based on helping others get through it.
- Try restarting the PC a few times to see if it can sign into your account.
- Check at C:\Users if you can see your old account with its files intact. If not check at C:\Windows.old to see if files were archived there during a version install that fails.
If so copy the files out externally so they are safe. Files should always be backed up if you value them at all. You can copy or drag them to an external USB flash or hard drive.
- From the temp account try to repair the old account using one of these methods:
https://support.microsoft.com/en-us/windows/win...
https://www.tenforums.com/tutorials/48012-fix-y...
https://winaero.com/blog/windows-10-youve-been-...
https://www.thewindowsclub.com/corrupted-user-p... (Avoid ad links which intrude into editorial copy, especially avoid Restoro ad)
https://support.microsoft.com/en-us/windows/fix...
- If not then you can try to create a new Local Administrator Account to see how it works: https://answers.microsoft.com/en-us/windows/for....
https://www.windowscentral.com/how-change-user-...
- If you cannot create a new account then to do this enable the built-in hidden Administrator used in emergencies like this, following Option Five here: https://www.tenforums.com/tutorials/2969-enable...
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 proceed to replace or repair the old 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 to enable the built-in Hidden Administrator following https://www.isumsoft.com/it/enable-hidden-admin...
- Sign into the now unhidden built-in Administrator account leaving password box blank, then create a new Local Admin account to replace yours:
https://www.isumsoft.com/windows-10/3-ways-to-c...
http://www.windowscentral.com/how-change-user-a...
- Sign into the new account, test it works and resolves the problem(s), if so you can move your files over at C:\Users.
- You can also try to repair the old Account by running a Repair Install by running the media you created earlier from Windows as shown here: https://www.yourwindowsguide.com/2016/06/how-to.... This reinstalls Windows while saving your files and apps in place; takes about an hour, resolves most problems. It also brings it to the latest version by the most stable method.
- If it doesn't fix the old account, when ready you can delete the old account by one of these methods:
https://www.tenforums.com/tutorials/5464-delete...
- Then if desired change it to a MS Account: https://www.tenforums.com/tutorials/5375-switch...
- 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.
If you have files that aren't backed up you can use the same bootable media to try to rescue your files using these methods: http://answers.microsoft.com/en-us/windows/wiki...
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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