When you want to schedule some not so important work you can have the option to lower the thread priority of a thread or you can change the base priority of the whole process. That can help to keep Windows responsive while CPU intensive tasks (e.g. some processes with Parallel.For instances) can use all cores if nothing else is going on. For that purpose you can change the process priority via SetPriorityClass or if you are using .NET you can use the Process.PriorityClass property to get and set ......