Controlling user access and permissions with XP Home vs. X..

Here's my problem, using XP Home: I'm trying set up effective porn blocking
on my home computer. No third party filtering software 'works' because they
can easily be circumvented through proxy sites and/or administrative access
to the registry, etc. Content Advisor on IE7, however, effectively blocks
proxy sites when you disallow unrated sites. GREAT! But, as long as a user
has access to the registry, they can allow unrated sites, even if they don't
have the content advisor password.

The catch is this: my family members MUST have some type of administrative
access in order to run the games/applications we want to run. Unfortunately,
XP Home only has limited and administrative user groups... which means it's
all or nothing. Using the "run as" option for applications is not an option,
as we are using the computer at all different times and the admin with the
password can't be around the computer all day and night.

Would upgrading to XP Professional enable us to grant users the program
permissions they need (or the programs themselves the permissions they need
to run even on limited accounts), while blocking access to registry files?

Many Thanks!