MFA,
Even if the built-in Administrator account was already enabled, you would still be able to use the a
net user Administrator /active:yes command without an error normally. The error you got below is for some other error instead.
System error 1359 has occurred
An internal error has occurred
With this error, I would recommend to see if doing a
system restore at boot using a restore point dated when you believe it was before this started. If that does not help, then you may need to reinstall Windows 7.