If the service installs properly, but fails to start, you can use the steps provided here to troubleshoot.
For additional details on using the Tomcat service and service monitor, see http://tomcat.apache.org/tomcat-6.0-doc/windows-service-howto.html.
As you are troubleshooting, check the log files (endeca-portal\tomcat-6.0.35\logs\jakarta_service*.log) for the relevant messages.
If the service will not start:
By default, service.bat looks for %JAVA_HOME%\jre\server\jvm.dll.
To change JAVA_HOME after the service is installed:For the bundled JVM, the file is endeca-portal\tomcat-6.0.35\jre1.6.0_21\win\bin\client\jvm.dll.
If you are not using the bundled JVM, then set the path to your JVM.