What Does the System Idle Process Do?

by Contributor

On a Microsoft Windows NT operating system (which includes Windows 2000, XP, Vista and Windows 7), there is a process called the "System Idle Process." It is something that many Windows users are curious about when seeing it in the system tool called the "Windows Task Manager."


To locate the System Idle Process, open the Windows Task Manager on a Windows NT operating system. In Windows XP, for example, press "CNTL-ALT-DEL" to reach the Task Manager. Click on the "Processes" tab and scroll through the list of processes until you locate the System Idle Process.


The System Idle Process, essentially, does nothing. It provides something for a processor to do when the processor is not being used for something important. Depending on the version of NT, the System Idle Process may actually run threads in the CPU which save energy.

System Idle Process CPU Usage

In the Windows Task Manager, the System Idle Process may occasionally appear to be using a relatively high percentage of the processor. In some cases, 90-100 percent. This is actually an indication of how much of the processor is idling and available for running applications.


A process is given a processor priority on a Windows NT operating system. This ensures that more important applications or services will be allowed to use the processor prior to another process. The priority of the System Idle Process makes any other process more important.

Fun Fact

Windows computer users who are new to the System Idle Process are often surprised to see a process using 90 percent or more of a computer's processor. They do not realize that it is actually the percent of processor available.


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