Raymond Chen has one artical posted on his blog that talks about how to tweak the network bandwidth Windows Automatic Update will use. It is very usefull on those systems that don't have Microsoft SUS or Microsoft WUS implemented. I quoted the full article below:
by Raymond Chen
By default, the Background Intelligent Transfer Service (BITS) which is used by Automatic Updates will use idle network bandwidth for downloading updates. This is normally not a problem.
One case where it can be a problem is you have a large LAN that shares a single DSL connection. BITS doesn't see that that DSL connection is shared. Consequently, each computer on the LAN will be using its idle network bandwidth to download updates and the total of all the LAN computers doing this will eversaturate the DSL connection.
Another example where this can be a problem is if you have a network card that connects to a hardware firewall which in turn uses a dial-up modem to connect to the Internet. (For example, you might connect through a classic Apple AirPort which is in turn connected to a modem.) BITS sees your fast network card and can't see that there is a bottleneck further downstream. As a result, it oversaturates the dial-up connection.
To tweak the BITS settings, you can fire up the Group Policy Editor by typing "gpedit.msc" into the Run dialog. From there, go to Computer Configuration, Administrative Templates, Network, then Background Intelligent Transfer Service. From there you can configure the maximum network bandwidth that BITS will use. You can even specify different BITS download rates based on time of day, so that it downloads more aggressively while you're sleeping, for example.
See the full article and all comments here