Need to Save Excel XML as just Excel file for user to open in Excel 2000
 

I have created a XML file using Excel 2003's XML formatting standards.
It opens great in Excel 2003, but Excel 2000 does not read it natively.
My question is:

1) Is there anyway to get Excel 2000 to read it natively?

2) If not, is there a way to save the XML on the server-side As an
Excel document for the user to download. I have the Microsoft Office
Tools for Visual Studio, but I need to use it in an already-developed
web application. Ideally it would be as simple as:

xmlfile.SaveAsExcel(filename)

I can easily do this in Excel 2003 manually, but I need this to be
generated server-side.

Any ideas?