It is probably easiest to ask each user to change their settings.
It is possible to programmatically change all user settings. You need to use impersonation to update each user's settings in turn, and the changes are to the usersettings entity. However, there are several attributes that you'd have to update, as CRM splits
the formatting settings across several attributes.
Or you could try the User Settings utility in XrmToolbox, though I'm not sure if allows bulk format changes
Microsoft CRM MVP - http://mscrmuk.blogspot.com/ http://www.excitation.co.uk