Games (The Sims 2) and Limited Accounts (Home version)

Why oh Why Cant Microsoft sort this out.

I have a home computer and I DO NOT repeat DO NOT want the kids having full
access accounts, so they have a limited account, but joy of joys, a new game
like The Sims 2 will not work at all in a Limited Account.
What is the point of running the game as an administrator when your are
giving them the password to your full account ( so mischief can be had by
bored fingers).

Why oh Why can't Microsoft DO SOMETHING about this Problem.

Can anyone come up with some ideas or programs that do a better job of
Limited Accounts than Microsoft.

Any Help would be gratefully received.