FWIW, setting JAVA_HOME wasn't enough for my Tomcat install

Yeah, I just reread the original post and realized that probably has nothing to do with it since it does work for him when he starts it from the command shell. Sounds like some weird windows thing where the environment variables aren't getting passed to services. You could test that theory by setting JAVA_HOME and any classpath you need from the batch script that starts tomcat. Beyond that I have no idea as I have never tried to use windows for a server.

-Mike