Reinstalling should be a last resort. Try rebooting with advanced options and restoring from a restore point before you removed the admin account. If that doesn't work, you can create a Windows 10 recovery drive, and boot from it. When you get to recovery options, choose Command Prompt and type the following commands (replace C with whatever your OS drive is if it's different):
C:
cd windows\system32
ren utilman.exe utilhold.exe
copy cmd.exe utilman.exe
exit
Now remove the recovery drive and reboot, and when you get to the login screen, click the ease of access button.
In the command prompt, type the following:
net user administrator /active:yes
If you want to set a password, type
net user administrator *
That's it. Now once you get in, rename those exe's: utilman back to cmd, and utilhold back to utilman.
Note: you can enable and disable boot devices, and set their priority, in your BIOS (usually). You can use the reboot with advanced options to get to the BIOS if you have UEFI, or just reboot and at the BIOS splash hit the appropriate key as shown on the screen.
Check here for what you can do to fix this: http://superuser.com/questions/1018064/windows-10-administrator-account-has-been-disabled-please-see-your-system-admin/1018080#1018080. See here http://superuser.com/questions/1093486/remove-main-partition-c-and-make-other-parition-d-the-main/1093497#1093497 for how to burn the ISO image from Windows 10 once you download it, it's a simple as that really.
– Pimp Juice IT – 2016-07-13T23:17:56.960Boot using the Windows 10 installation media, and access recovery options. Then do a System Restore rollback Lost Admin Password or Privileges, and User Account Locked out? WinRE can Rescue You won't be asked for the password if you boot from the install media.
– w32sh – 2016-07-13T23:41:44.007