"Colin Hayes" wrote:
I did download and install these :
Microsoft Office Compatibility Pack (FileFormatConverters.exe)
Microsoft Office Compatibility Pack Service Pack 3 (SP3)
and also Excelviewer.exe
It's just that I don't see anywhere within excel 2003 to save
as xlsx if I open a workbook and try to save in this format.

Hmm, something is wrong. I don't know what it could be.

After I installed the Office Compatility Pack, .xlsx and .xlsm (et al) did
indeed appear in the choices in the Save As dialog box. I think this was
all automagic. I don't recall doing anything special. But it was a long
time ago.

The only thing I can imagine: do you have the Excel (or Office?) 2003 SP3
service pack?

If not, I would uninstall the Office Compatiblity downloads, update to Excel
(or Office) SP3, then re-download and install the Office Compatilibity
Packs.

If that does not work for you, you might SOL. At least, I am out of ideas.

PS: I would uninstall the Excelviewer. If you have Excel 2003, I cannot
imagine why you would need the viewer. I wonder if installing the viewer
after Excel 2003 is causing some confusion in what to load when you click on
an Excel file or otherwise start Excel. I don't know; I have no knowledge
of or experience with the viewer.