>I have the ds, and I make an XML file to pass or do I make a string of xml?

Sounds like you have a dataset already on your client which assumes that you are using a .net client. You can continue to pass datasets to/from your webservice as long as you are in control of both ends of the wire. The minute that you have a client that doesn't know about a dataset (java for example) then your path of least resistance is to design a wsdl contract that is more amicable to a variety of front ends.

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>And how does my WS catch in on the receiving end? This is a registration component, where your install fires off who you are and what types of business with our products you are dealing with back to us.
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Surely you must have heard about SOA and contract first web services. If not check out http://www.mindreef.com/newsletter/newsletter-v6.html. Get yourself some kind of WSDL editor (SOAEditor or XMLSpy). There is even an addin that generates code form your wsdl http://weblogs.asp.net/cweyer/archive/2003/10/22/32930.aspx
That will lead you away from the dataset and towards interoperability.