Locked out of Windows 10: login no longer shows Administrator, but only an account that I never used

I downloaded and updated my Windows 7 pro to Windows 10 today. I had two user accounts in Windows 7 before update; Administrator and Ritesh. I never used Ritesh account, so over the time I even forgot that I had this account, and now I don't remember its password. After update to Windows 10, I can see only Ritesh user in login screen. I tried several combination, but they didn't work. I tried going into safe mode, but again it shows only Ritesh user. Setup didn't ask for Microsoft Account during installation, but I did reserve the update using Microsoft Account.

My USB ports are not working so only option I have is CD/DVD recovery.

I tried Reset option as well, but it also asks for Ritesh account verification.

How can I log in using Administrator account as I do remember this account's password?

I'm providing this answer as an alternative to watching OP's video and in case the video ever goes down.

It sounds like you're looking to enable the administrator account again. If you cannot sign into Windows at all, have no other boot devices, and want to use no software - do the following.

1. Click/Tap on the Power button under the Start Menu or on the lower right-hand side of the Login screen, press and hold the Shift key, and click/tap on Restart. This will open a command prompt at boot.

Then type:

net user Administrator /active:yes

If for some reason that doesn't work, do the following:

2. In the command prompt, type regedit, and press Enter.

3. In the left pane of Registry Editor, click/tap on the HKEY_LOCAL_MACHINE key.

4. Click/tap on File (menu bar), and on Load Hive.

5. Open the drive (ex: D ) that you have Windows 10 installed on, and browse to the location below. NOTE: The drive letter (ex: C) will not always be the same at boot as it is from within Windows 10.

            D:\Windows\System32\config
   

6. Select the SAM file, and click/tap on Open.
7. In the Load Hive dialog, type REM_SAM, and click/tap on OK.
8. In the left pane of Registry Editor, navigate to and open the key: HKEY_LOCAL_MACHINE\REM_SAM\SAM\Domains\Accounts\Users\000001F4
9. In the right pane of the 000001F4 key, double click/tap on the F binary value to modify it.
10. In line 0038, change 11 to 10, click/tap on OK.
11. Close Registry Editor and the command prompt.
12. Click/tap on Continue to startup back in Windows 10.

NOTE: To disable the Administrator account simply reverse Step 10.

you need to have the Windows (7|8|8.1) install media available.

1. Start your PC off the (Disk|USB|HDD) that contains the install media
2. Once loaded, press Shift+F10. This will open a command prompt
3. Run the following commands in order:

diskpart list vol

1. Once you find the right volume (your C: drive (it may have a different drive letter)), run exit
2. Now, run D: where D is your drive letter.
3. Run cd \Windows\System32
4. Run ren Utilman.exe Utilman_old.exe
5. Run copy cmd.exe Utilman.exe
6. Reboot

Once you get to the logon screen, click the Accessibility Options icon. Once the Command Prompt opens, run these commands, replacing user_to_change with the user you want to reset the password of:

net user user_to_change *

Enter a new password, enter it again (you won't see it) and log in. You can now go back to C:\Windows\System32 and delete the Utilman.exe that we made, and rename Utilman_old.exe to Utilman.exe

For those who are looking for answers:

I followed this video until Command Prompt after login screen (5:05). https://www.youtube.com/watch?v=0dfEd4HZyV4

Then executed this command in opened command prompt.

c:\>net user Administrator /active:yes

And then restart the system. After reboot, it showed Administrator account and I am able to login. Don't forget to rename the executables back to their original form.

1. Click on the Power button under the Start Menu or on the lower right-hand side of the Login screen, press and hold the Shift key, and click/tap on Restart. This will allow you to open command prompt at boot.
2. On the cmd window type following command net user Administrator /active:yes

3. In the command prompt, type regedit, and press Enter. Navigate to the following key:

   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WindowsNT\CurrentVersion\Winlogon

4. Create another key under Winlogon called SpecialAccounts (case sensitive) and under SpecialAccounts on more key called UserList (case sensitive). Under UserList key create a dword value Administrator and provide 1 as value data. After you'll finish it's suppose looks like this:

HKLM\SOFTWARE\Microsoft\WindowsNT\CurrentVersion\Winlogon\SpecialAccounts\UserList

"Administrator"=dword:00000001

5. Close Registry Editor and the command prompt
6. Click on Continue to startup back in Windows 10