The Microsoft File Format Convertor only allow the opening of Office 2007 or 2010 files in earlier versions of Office. Your 1997 spreadsheet should open in 2010 without a problem unless M$ have barred really old versions from the new club. Can you please post back the error message you're seeing?
If you have an urgent requirement to see that file, download OpenOffice which is free of charge and will work with your spreadsheet. Download it from http://www.openoffice.org.
Not sure if format converter will do it but if not open it in an office 2003 program then select save as office 2003 document, then open with office 2010 and select save as office 2010 document and you are good to go.