Archived from groups: microsoft.public.windowsxp.basics (More info?)
Windows XP is written in specific language versions, therefore one
cannot change it from one language version to another. You'll need
to purchase a "Full Version" of Windows XP in the language version
you desire, reformat your drive and install it "clean".
Or if you have an available empty drive or partition, you can install
another "Full Version" of Windows XP in a different language version
and create a dual-boot configuration.