Build an Excel spreadsheet application with the power of PHP and XML

I have developed a web system using the same mechanism as the topic in this site ‘Build an Excel spreadsheet application with the power of PHP and XML’ and it works fine BUUUUUT it doesnt work in some computers.Is there any specific specification of the system needed like there should be excel (2002/2003) on the system,it should be XP operating system….

Thanks