We are hosting lot of Win 2008 servers, now I am aware of commercial bandwidth monitoring tools, but I know there are some network tools available in Windows server like NetMon etc, I dont know how to use them, I am sure Windows 2008 Web Edition should have something inbuilt tool.. or else we have to realy go and buy one..
SnapOverflow
In the administrative Tools folder (in the start menu) you'll find performance monitor. That will let you monitor network traffic (as well as thousands of other metrics) either in real time, or to log to disk, or to a database for later viewing.