Help with admin for Mackbook

I accidentally erased the admin for a macbook, iOSX5... Also managed to deactivate the root admin... so ive been trying to give aministrator privilages to the user via SUM, but ive failed to do so...
Any ideas?
Thanks...

Given the amount of damage you've already done, I'd say "stop digging" would have to be my advice.

I have no idea what IOSX5 means, so I'd just suggest that the user back up their personal home folder (which presumably has already been done), boot from the recovery partition or the system DVD and start over, restoring their user folder when prompted to in Migration Assistant as the new system is being installed.