(1)What exactly do you mean by "test enabling and logging."
The Administrator account is generally disabled, you can't 'see' it. You'll have to enable it using the Tweak UI tool (
http://www.microsoft.com/windowsxp/downloads/powertoys/xppowertoys.mspx).
(2)When you say "Install and register from there". Do you mean Avast?...or are you referring to the utilities on the link you put below?
Yes, I mean, log into the Administrator account, install avast e register (insert the key) there.
(3)Avast has installed (and works) on an Admin. account. Is it possible that this can happen but it is not the TRUE admin. account?
avast can be installed and works in an admin account and any other user account. The problem could happen when you have more than one account with admin rights. In this case, maybe, using the real Administrator account could help.
(4)How do I find the real admin. account?
I've posted two links and hope you get it