Within the focus program when you say
ON TABLE PCHOLD FORMAT EXCEL
the report opens in excel and then when you do a File, Save As the default file type is Microsoft Excel 2.1 Worksheet.

Within the focus program when you say
ON TABLE PCHOLD FORMAT EXL2K
the report opens in excel and then when you do a File, Save As the default file type is Web Page.

Does anyone know if the default Save As file types can be changed ?

The problem is that WebFOCUS has no control over the default filename (there is nothing in the HTTP protocol that allows it to be set).

Do you know what controls this ? Is it an excel setting ?

In Excel, go to Tools->Options. Navigate to Transition tab. Change the setting for "Save Excel files as:"

Does this help?