If Tomcat is installed but not starting, refer to Tomcat's log files to see if there are any errors. Specifically, have a look in the files called
where [tomcat] is the folder where Tomcat has been installed to (e.g. C:\Program Files\Apache Software Foundation\Tomcat 6.0) and yyyymmdd is the date.
If you see errors like this:
[174 javajni.c] [error] The specified module could not be found.
[947 prunsrv.c] [error] Failed creating java C:\Program Files\Java\jre1.6.0\bin\client\jvm.dll
[1202 prunsrv.c] [error] ServiceStart returned 1
The solution is to copy the msvcr71.dll file from the Java folder to your [windows]/system32 folder. For example, copy the file