>I created a WinForm form from the out-of-the-box base form. How can I now re-define it to be based on a custom form clas my own class library that I want to build?
>
>
>Where would I go to tell the form what it is based on?

It is in the class definition

using MyClassLibrary;

public class myForm : MyClassLibrary.MyOwnFormBase
{
}

Or if VB

Imports MyClassLibrary

Public Class myForm
    Inherits MyClassLibrary.MyOwnFormBase

End Class

Is this what you mean?
Tim