For example, maybe XlExcel8 is defined for Excel 2010 (which is installed on the original system), and has a different name in Excel 2003 (installed on the Windows XP system)?
Somehow I totally overlooked that the error message in your original post was complaining about "xlExcel8". Combined with the fact that you're using Excel 2010 and Excel 2003, I think I know what's going on. The problem is not with the use Win32::OLE::Const 'Microsoft Excel'; line at all.
Starting with Excel 2007, Microsoft introduced a new Excel file format and used .xlsx file extension as the default file extension for the new file format. Also, with Excel 2007 and Excel 2010, the default file type when saving a file is the new file type. The user can still choose the older file type if he/she wants to.
Since you're not providing much code, I have to make some guesses. I'm assuming that you've developed your code on your system with Excel 2010 and wanted to save in the older Excel file format. In that case, you have to specify the file format when saving the file. That's where you're using the xlExcel8 constant. However, that's not a defined constant in the Excel 2003 OLE library. Although there is a free update to Excel 2003 that allows it to use the new file format, I can't say for sure if that will add the xlExcel8 constant to the Excel 2003 OLE library.
If you're planning to have a script that works with Excel versions 2003, 2007 and 2010, then you'll probably need to check to see what version of Excel is installed in order to know which save methods to call. The way that I've done that before was to look at the code from the OLE browser from the Win32::OLE module to see how it dynamically pulled out information about the available OLE libraries. Then I wrote a subroutine that looked for the "Microsoft Excel X.0 Object Library" and used the X value to determine the Excel version. Excel 2010 is 14, Excel 2007 is 12, and I believe that Excel 2003 is 8.
Here's how to do a quick test of my assumptions. If my assumptions are correct, you probably have something like the following in your code:
$book>SaveAs({Filename => $filename, FileFormat => xlExcel8});
On your Excel 2003 system, try changing that line to the following:
$book>SaveAs({Filename => $filename});
If I'm right, that should work on your system running Excel 2003.
