Archived from groups: microsoft.public.windowsxp.basics (More info?)
Microsoft Office 2003 is not an "operating system". If you meant you
cannot install an English version of Microsoft Office 2003 on a Spanish
version of Windows XP Home Edition, that's because you'll need
a Spanish version of Microsoft Office.
On the other hand, if you meant you cannot upgrade a Spanish version
of Windows XP Home Edition to an English version of Windows XP
Professional, that's because it is not a supported upgrade path. You'll
need to purchase a "Full English Version" of Windows XP Professional
and proceed with a "clean install".