How to investigate intermittent Windows Server "logon failure" problems?
If those windows servers are members of a domain then it's possible that some group policy is overwriting this "logon as a service" local policy.
It is not required to restart Apache HTTP Server in order to reload the configuration, you can just run
C:\Apache24\bin\httpd.exe -k restart
This way, only child Apache HTTP Server processes will be restarted and your server won't miss a request.