Ummm...I assume you really mean from an HTML form. The page that creates the form might be written using ASP, but the form itself is clearly HTML, no?
So you are saying you have
<FORM Action="processThisForm.asp" Method="POST">
and you want to convert the fields of that <FORM> to XML?
Do you have a pre-defined XML format you need to use? Or can we make one up on the fly?