The PriorityClass property controls the priority class of the new process (used to determine the scheduling priorities of ...

The PriorityClass property controls the priority class of the new process (used to determine the scheduling priorities of the threads in the process).  If the PriorityClass property is left null, the priority class defaults to Normal unless the priority class of the creating process is Idle or Below_Normal. In these cases, the child process receives the default priority class of the calling process. One of the following values can be specified: High - Indicates a process that performs time-critical tasks that must be executed immediately for it to run correctly. The threads of a high-priority class process preempt the threads of normal-priority or idle-priority class processes. An example is Windows Task List, which must respond quickly when called by the user, regardless of the load on the operating system. Use extreme care when using the high-priority class, because a high-priority class CPU-bound application can use nearly all available cycles.  Only Realtime priority will preempt threads set to this level Idle - Indicates a process whose threads run only when the system is idle and are preempted by the threads of any process running in a higher priority class. An example is a screen saver. The idle priority class is inherited by child processes. Normal - Indicates a normal process with no special scheduling needs. Realtime - Indicates a process that has the highest possible priority. The threads of a real-time priority class process preempt the threads of all other processes, including operating system processes performing important tasks, and high priority threads. For example, a real-time process that executes for more than a very brief interval can cause disk caches not to flush or cause the mouse to be unresponsive. Above_Normal - (Windows 2000 and later) Indicates a process that has priority higher than Normal but lower than High. Below_Normal - (Windows 2000 and later): Indicates a process that has priority higher than Idle but lower than Normal.