I have a friend, (totally computer illiterate!), who's got XP Home with three users. Somehow, when the system was set up, the 3 users got denied permission to use Outlook Express. How do you go about changing permissions in XP Home?

(I'm a sole domestic user so I'm just not into this whole Administrator/User/Permissions business - I've got XP Pro and the problem would seem relatively easy to fix under that.)