Running Demo on a user acount in XP

I installed the demo on a machine with two accounts : administrator and student. In the admin account the demo runs fine, but in the student account the GUI doesn't change after lighting the mission ( it still shows the dialogs ), it shows the HUD but it doesn't render the scene.

Any hints on what may cause that ?

I already checked the file permissions. I'm not a Windows guy ( I'm a mac user ) so I haven't had much luck figuring this out.