My application allows data to be exported to Excel. I wrote it on a computer with Excel 2007 so it exported files as *.xlsx by default; now I'm opening it on a computer with Excel 2003 and of course that doesn't work and I need to export as *.xls.

My question is: Can I detect the Excel version so that I can automatically have the export form default to the correct filetype?

(Side question: When I originally wrote it on the other computer using Visual Basic.NET, I needed to import Microsoft.Office.Interop. Now, working on it from a different computer using Visual Studio 2012, I don't need to anymore and it yields a warning. Why is that?)