Somewhat [OT] : cgi, XML and Excel files

[jbv]

Hi folks,

I've just finished a Rev cgi script that outputs sophisticated
Excel files (with layout, styles and stuff) using the MS XML
format.
On my Mac and my PC everything works fine, but I'm using
openOffice instead of excel.
I've asked a few potential users to test it, and some of them
meet various problems, like the XML code being opened in
Word instead of excel, or excel displaying just crap...
As often, I don't have access to all kinds of potential users,
as they are spread all over the country, only through a few
managers who don't know a bit about technology and have
no idea what versions of excel and windoze end users may
have on their laptops...

So here's my question : does anyone have a clear idea of
which versions of excel support that MS XML format ?
The various infos I grabbed on the web aren't clear : it looks
like XML became available with Excel 2003, but is it ONLY
Excel 2003 or any version SINCE Excel 2003 ?
Any additional info will be apreciated too...

Thanks for your help.
Don't hesitate to reply off-list if you think this is OT...

Best,
JB