Once I restarted my PC, then Apache 2.25 rejected to work anymore. I went to the system service administration, found couldn't get Apache service started.
The possibility that the port Apache commonly using occupied by other processes is excluded. Actually the port was used by Adobe Flash Media Server, but I terminated all the related services and made sure the port was available but I still couldn't startup it. Then I went through httpd.conf again, all the configs remain the same as it works normally before, and nothing wrong was feedback from the Apache logs.
Can anyone can give some clues to repair it?
If your apache is not starting with httpd.exe, Then there could be many possibilities. Try to start the httpd using console (command prompt)
cd "\Program Files\path_to_apache_installation\Apache2.2\bin"
httpd.exe
If the apache console stops right away, Check the apache logs for some clues
cd ..\logs
more < error.log
The logs will convey you more details why apache is not starting