"Not Responding" Message in Windows Form Application

Question

When there is a statement in a windows form application which is executing in an infinite loop, the name of the form will show "Not Responding". How does .NET determine if the application is in an unstable state? I wonder if WMI is the right way to track the application? If so, what is the right way to start? If not, is there a way to determine the unstable state of an application? Welcome any advice