Locked out from Windows 8.1 administrator account being disabled

I installed a Windows 8.1 laptop.
By default the Administrator account is disabled. During the install process, the user created belongs to the administrators group (call it FirstUser).

I installed various software, I created a normal account for the user (call it RealUser), and I mistakenly deleted FirstUser account (while I was connected under this account). I rebooted and... oh well, I understood the mistake. I no longer have access to any administrative privileges.
The laptop is still in workgroup.

I tested with Offline Windows Password & Registry Editor (latest version):

1. Activated Administrator account, and blanked its password (no option to set a new one)


2. Gave RealUser account administrative privileges

After reboot, only RealUser account is still available.
Once logged in, I'm unable to access anything requiring administrative provileges.

Does anyone know a way to successfully activate the Administrator account, or whatever ?

Answer

If using the relevant utilities in HBCD or Win7Live (from reboot.pro) doesn't help for some reason, you could try replacing the sethc.exe (from an external OS of course) like in this tutorial:
http://4sysops.com/archives/forgot-the-administrator-password-the-sticky-keys-trick/