i have a really good and effective solution to your little prob, follow this one:
go to>>control panel>>regional language option>>language tab>>check install east-asian language. click apply to continue, if it asks you for the CD of XP, put the CD and let it install. then restart.
also, so that you can see the KATAKAN/HIRAGAN/KANJI writings and characters on the webpages and forums that poeple type, follow this one too:
go to>>control panel>>regional language options>>advance tab>>SET language for non-unicode programs to: japanese, if it asks you the CD XP, put the CD and restart.
now your OS is fully equiped with asian characters and letters after restart.
dont worry about the WINDOW's interfaces, your windows will be always in ENGLISH characters, only the your OS will now be aware of asian languages.
dont forget to add this up:
go to>>control panel>>reginal language options>>language tab>>click DETAILS button>>go to installed services>>click ADD>>select japanese IME then APPLY.
after that you will notice a 2 letter on your right system tray with "EN" - means english, now if you want to type japanese just click that "EN" and change to "JP", then click again "JP" and select "show language bar", and change the letter "A" to あ or any of those settings, so that you can type hiragan and katakana along with kanji too.