Windows 2004? U mean Win 2003? Longhorn isnt out until 2005 I think? From my experiences I feel Hosting Controller is flexible , easy to use and save me a lot of time manually creating accounts. Feel it is the best in its category.
My vote also goes to HELM (http://www.webhostautomation). We are also using this for our Web Hosting Services though it lacks some basic things also like when once of your shared hosting uses over bandwidth/space he is not notified and his acccount is not suspended automatically.
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