XP is by far the simplest of the Windows operating systems for switching between multiple languages. Let's say you want to switch to Japanese:-
Open "Regional and Language Options" from Control Panel
On the first tab, select the language "Japanese", for our example.
Click on the "Languages" tab. If you will be typing in Japanese, then click the [Details] button, and select "Japanese" as the "Default input language" and click [OK].
If you will only be compiling in Japanese, then you do not need to change the Default Input Language. Note: If you have not already done so, and you are compiling for an Asian language, please ensure that the two checkboxes for Supplemental Language Support, are checked.
Now click the "Advanced" tab and select "Japanese" as the "Language for non-Unicode programs". You will be asked if you want to use the existing files installed. Answer Yes if you do and then answer Yes to reboot.
That's it, after you reboot you will be able to load Fast-Help and compile your project in Japanese.