Managing a Windows network starts by ensuring that every machine is kept current with the fixes provided by Microsoft. To do so, you have several choices.
First, you might decide to manually browse to
http://updates.microsoft.com on each computer on your network. This solution, though very functional, is labor intensive.
Second, you might set Windows Automatic updates to pull critical updates from Microsoft's site and install them automatically. An even better solution; but one that has two small draw backs. First, not all updates can come down via this method, and second, if a machine develops a problem with the automatic update service there is no way for the administrator to know this without manually checking the machine on some scheduled basis.
Third, you might setup a Windows Software Update Server. This is a great option, allowing you to monitor which updates are being installed and which machines are getting them. It can be configured in various manors, anywhere from giving the administrator precision control to an environment that is very automated. Whichever method you prefer, we'd be happy to help you design and implement a strategy that will service your environment.
Forth, perhaps your organization isn't large enough to merit installing such a server, but you want the benefits of having one, let us host and manage an update solution for you.