How to share programs across users

Hi - I am new to Vista.  I have set up 5 user accounts, one for each family member on the new PC. 

If I install a game eg (SIMCity) on one user, how do I share it across the other 4 uses?

I have set up the users as one admin and 4 standard

Its vista home premium 32bit

Sorry if its a basic question, I did try the help and support but that was focused on sharing across a network !!!

Rob