Vista - separate user accounts

My 250 gig hard drive has 3 separate user accounts; mine (admin) Clare and Lauren. Why is it when I install a program on mine, it appears on their's? I thought with 3 separate accounts programmes would stay separated. Forgive my ignorance or naivety for asking this, not too many sarcastic comments for what may appear a rubbish question.

Hello Skeletor,

When programs are installed on the computer, they are installed for all users to access unless the program has a option during installation to select what users can use the program.

You can remove the program's shortcut from the All Users Start menu and C:\Users\Public\Desktop locations to not have it there for the other user accounts, but they can still access it by default in the C:\Program Files folder.

You can also change the permission level of the program's exe file to Deny access for a specific user to. You can use this tutorial below as a guide for this. Be sure not to deny all users or your user account to prevent blocking access for you as well.

Folder Permissions

Hope this helps,
Shawn