Group Strategy Windows 2008 Server

Hello,

Configuration: Windows 2008 TSE Server, single domain, single server, 15 XP clients

I need to create a group strategy (or to change an existing group strategy) so that for all users (TSE and non TSE users) Internet Explorer connection goes trough a Proxy and that users cannot disable the proxy settings in IE

How should I do?

Another question : do you have a simple paper explaning basically how to change or built a group strategy in Windows 2008 environment ?

Thanks