Is the file a defined MIME type in IIS6? If not, IIS6 won't serve it up, while IIS5 did with no questions.
See: http://support.microsoft.com/default.aspx?scid=kb;en-us;326965

>>From Windows Explorer should work.
>
>I think we are miscommunicating. I can access the file from Windows Explorer, but I want IIS to serve up the file since this is part of a web application.