今天打開Apache的時候報錯：
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
是系統的服務占用了80端口，所以要么結束系統服務，要么修改apache端口。
PID4的服務是World Wide Web Publishing Service
這里選擇結束這個系統服務，運行services.msc，找到然后停止即可。防止下次開機再出現這種情況，在屬性里可設置成手動啟動。