Excel 2007 ate my fields

[PaEyer]

When I try to update a pivot table (created in Excel 97, later updated in
Excel 2003) in Excel 2007, some of the fields from the source database are
not available. (Plus it offers fields from other sheets in the workbook, but
that's another issue.) It's the same when I try to create a new pivot table
- all the fields I need aren't listed. How can I get it to recognize all the
fields; or, alternatively, how can I redefine the data I need as a field that
will show up in the pivot table field list?

Thanks.