Can a standard user access the Admin account via Safe Mode?

I have a situation where I want to be the administrator for my son's
laptop, and convert him to a standard (non-admin) account. He originally
set up the laptop, giving himself admin privileges, but he is no longer
allowed to use it in that condition :(

I am now the passworded local admin account (same account used to
install Vista), and AFAIK do not have the system Administrator
(upper-case A) account activated. He has a "standard" account. However,
he is clever, and will try to work-around to get admin access. I've read
the "recover password / activate Admin /etc." links in the forum, and I
have a few questions:

1. Can my local admin account OR the system Admin account be accessed
and altered by a standard user in Safe Mode?

2. Is it possible to block Method 3 (DVD boot for password reset) if
the system is already properly set up for one admin's access?

3. I do not see the "user groups" folder in Comp Mmgt Control Panel to
enable or disable the system Admin account. How can I check its status?

BTW, I'm using Vista Home Basic.