strix 0 Newbie Poster

I need to configure a small office network not in domain for time sync. All computers are with Windows XP Pro. I want one of them to act as network time server and others as a clients. I need client time polling interval to be less than a week, i'd say about 4-8 hours will be fine. What should I do? Please help!
Do I need external time server software like this or can achieve same thing with Group Policy Editor?