I don't have much experience of server admin, so please forgive me if this is a silly question!

I want to change the default application for opening image files on the Windows 7 computers in our ICT suite when pupils are logged in - at the moment they open in Colour Magic which isn't ideal. I have tried logging in as administrator on one of the machines and changing the preference, but this only changes the admin account. The pupil accounts are locked down so that they can't right click or access any controls, so there is no way to change the setting once they are logged in (and in any case this would presumably have to be redone for each different pupil account).

I am hoping that there is a simple way to set the default application using Group Policy or a login script, but have not had any luck searching Google for one. Any ideas would be much appreciated.

Thank you.