system services not appearing in group policy

The group policy editor will only show the services that exist on the computer you are editing the policy from. If you want to disable services that don't exist on that system, you'll want to create a security template from a computer that has all of the services you want to disable instaled on it. http://www.tech-faq.com/understanding-security-templates.html has a good explanation of Security templates and how to work with them. Once you create a security template from any computer it can be imported to a GPO and deployed from there.