Increase Java memory when running as service?

Search yielded nothing for me.

Can someone please tell me how to increase the java heap size when running Messenger as a service using messenger-service.exe?

Is there a recommended size for ~500 users? Machine is P4/1GB RAM.

Thanks,

Sean

this is a solved method.

http://www.jivesoftware.org/forums/thread.jspa?messageID=96489&#96489