Hi Rajan. 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...
Next try enabling the Hidden Administrator account to log into and set up a new Local Administrative Account to sign-into, move files over and set up, using Option Five here:
https://www.tenforums.com/tutorials/2969-enable...
To do this you'll need to access a Command Prompt in repair mode using whichever method works here:
https://www.tenforums.com/tutorials/2294-advanc.... You can also try the option to System Restore. If you don't have the password this may be limited to using the booted media.
If necessary you can create Windows 10 Installation Media on another PC:
http://windows.microsoft.com/en-us/windows-10/m...
Insert media, boot it by powering up PC while pressing the BIOS Boot Menu Key:
https://www.sysnative.com/forums/hardware-tutor...
Choose the boot device as a UEFI device if offered. 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.
After it loads, on second screen, choose Repair Your Computer, then Advanced Troubleshoot Options to try System Restore, or if that fails the Command Prompt to enable the Built-in Admin account .
If this fails from the Troubleshoot Options try a Reset, saving files.
If this fails choose Install Now, then Custom Install, then at 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. Follow the illustrated Clean Install steps in this tutorial which compiles the best possible install that will stay that way as long as you stick with the tools and methods given:
http://answers.microsoft.com/en-us/windows/wiki...
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 having the full range of options 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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