Detecting the Idle State
In Windows 7, the Task Scheduler verifies that the computer is in an
idle state every 15 minutes. Task Scheduler checks for an idle state
using two criteria: user absence, and a lack of resource consumption.
大意就是:在Windows7中,系统每隔15分钟检查一次系统是否处于空闲状态,判断都条件有两个:一是用户不在,而是系统资源没有被使用(例如CPU利用率什么的)。具体内容可以参看微软都文档地址:Task Idle Conditions