Excel 5 sounds pretty old to me,
and some people accuse ME of being
stuck in the 1940's.
Typically, though, the rule is you can
covert an older version to a newer version,
but not visa versa.
If you know where the version 5 spreadsheets
are, you should be able to open them in Excel
2003, and choose "Save As" Excel 2003 spreadsheet.
Hope that works.
Dennis in Las Vegas.