One of our customers is still running Office 2003, but wants to use Excel Services. There seems to be some confusion if this is possible or not. As far as I am concerned, it is very well possible, although there are some prerequisites, and some limitations. These are my observations from an end user perspective:
- The files in SharePoint need to be in .XLSX or .XLSB format, it does not work with .XLS. You can install the Office File Converter pack, which will allow Excel 2003 to save files as xlsx.
I had some issues installing it, but installing Service Pack 3 of Office 2003 fixed all issues.
- With Office 2003, you can not limit the display of the workbook in Excel services to a specific area (worksheet, named range…). It always displays the full workbook if you open the file in Excel Services. In the Excel Web Access web part, you can limit the display to a worksheet or a named range.
- Office 2003 can not work with parameters, that allow you to change certain values dynamically in the worksheet (e.g. using filter web parts).