I have done more reading since posting this. Now I understand that - just because the file has the extension (.XLS) does not mean that it created an Excel file. It created an ASCII file that I can open in Excel. In testing we changed the extension to (.XLSX) on the Linux side, the file could not be opened in Excel anymore. It gave us a warning, we clicked OK, but nothing opened.
So we put it back to (.XLS) and now staying with that. Once we get the file over to the PC side, I suggested writing code that would save the file as an (.XLSX) file.
ODS HTML, ODS CSV and ODS TAGSETS.EXCELXP all create different types of ASCII text files (HTML, comma-separated and Spreadsheet Markup Language XML) that can be opened and rendered with Excel. The XML created by TAGSETS.EXCELXP is Office SpreadsheetML version 2002/2003.
The new .XLSX files are a different type of XML -- in fact, an XLSX file is not actually ONE file, it is an archive of files. If you perform the "experiment" described in this previous post: http://support.sas.com/forums/thread.jspa?messageID=18646䣖
of renaming an XLSX file with the extension .ZIP, you will see the new structure.
Microsoft is very picky about which file extensions you use -- so naming an HTML file with a .XLSX extension is not going to make Microsoft happy to open the file. With Office 2007 in particular, even naming an HTML file with a .XLS extension or naming a 2003 XML file with a .XLSX extension causes Excel to complain upon opening the file.
Your approach of creating the HTML file and then having a program do a SAVE to the format you want is a good approach. Or you could educate your users ....