If you are using Windows XP, and if the network is on a domain (not a workgroup) you should be able to control what updates pass info a system.
There is an administration for the domain computers (its accessible through your web browser, but, unfortunately, I dont know the address.)
It allows you to select if you want to have the computers just access via Microsoft, or your own servers, also lets you select the language.
Anyone know what I am talking about? (Starts with an S)