今天打开Apache的时候报错：
22:15:30 [Apache] Problem detected! 22:15:30 [Apache] Port 80 in use by "Unable to open process" with PID 4! 22:15:30 [Apache] Apache WILL NOT start without the configured ports free! 22:15:30 [Apache] You need to uninstall/disable/reconfigure the blocking application 22:15:30 [Apache] or reconfigure Apache and the Control Panel to listen on a different port
是系统的服务占用了80端口，所以要么结束系统服务，要么修改apache端口。
PID4的服务是World Wide Web Publishing Service
这里选择结束这个系统服务，运行services.msc，找到然后停止即可。防止下次开机再出现这种情况，在属性里可设置成手动启动。