Using the NDTU console you can select a sickly Windows Server and view its services, furthermore, you could start or stop a service if that would cure the problem. Another troubleshooting technique is to look for errors in the event logs, or run native Windows tools such as Perfmon.
Troubleshooting server problems can be time-consuming. Under the pressure of fixing the servers before the users complain, or the boss finds out, you don't want to waste time connecting to the servers, and then loading tools to fix the problem. Thus it's best to just launch the DNTU and start collecting information.