I did a few checks:

Default format (Excel Options): Excel Workbook

Activeworkbook.SaveAs "c:\temp.xls"
(not specifying fileformat, specifying 'wrong' extension)
in Excel2007 saves with xls extension in xlsx fileformat without
warnings. (same if you use .txt extension)

Activeworkbook.SaveAs "c:\test" Saves C:\Test.xlsx

the xls will open without errors in Excel2007,
but must be renamed to .xlsx to open in Excel2003 (with converter)


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keepITcool
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Jim Rech wrote in

Too bad. I use that even though a save resets the used range too. I
doubt it's a bug in the MS sense though. Have you reset your default
file save as file type? I had to change to this to not error:

ActiveWorkbook.SaveAs "c:\temp.xls", xlExcel8