Automating a change of proxy server

We currently run Internet Explorer 5.0 on several hundred PC’s in the organisation. We need to change the current connection to point to our new proxy server (eg current connection is to server1 needs to be changed to server2). Is there any way thiscould be automated (maybe by changing the registry setting).
I know it would be relativly simple to e-mail each user with step by step instructions to manualy change the setting. But if there is a simple (and easy!) way to automate it It would makea more elegant solution.