I believe that is not possible to change language. It works only from english to others, not vice versa.
You can try , installing the microsoft language interface pack and maybe I am wrong with "vice versa".
If your computer is under warranty, you can always "Ghost" the C: partition ( under which you have XP installed ) and put the ghost image on some DVD or another partition, and install another XP PRO SP2 or whatever you's like and in case of problems with hardware u format C and restore the ghost image to C so that you will have the "original" xp when you'll go with pc to be repaired.
But it's better to install Xp from 0.
-reply by Cornel













