Are you interested, for example, in typing out a document in Word and having your romaji input convert to hiragana/katakana/kanji?

If so, you simply need to install Japanese IME on your PC (I’m sure it’s something similar on a MAC). It’s totally free.

Here is a post I found that provides instructions: http://www.declan-software.com/japanese_ime/

Let me know if that is what you were looking for. If not, I would be happy to look into this further.

For PC (Windows XP)

Go to Control Panel > Language and Regional Options > Add Other Languages Click "Install files for East Asian languages" and apply. Click "Details" in Txt services and input languages Select JP (Japanese) / Keyboard / Microsoft IME Standard 2002 and click "Add". Also, go to Language Bar settings and select the options you like. It's convenient to have the input icons in the task bar or desktop for easy access.

For Mac (OS 9 and up): GO to System Preferences > International > Input Menu. Select Kotoeri (Hiragana, Katakana and Romaji). Click "Show input menu in menu bar" for easy switching between English and Japanese input methods.

For both PC and Mac, chose Hiragana as a default so that you can type in Romaji (spell Japanese words phonetically using English alphabet) and Hiragana will show up. If you need to convert Hiragana into Kanji, you can use the space bar to choose the correct Kanji from a pop-up window.

Good luck.

If you're looking for an specific word processor just for Japanese, NJ Star is really good, and easy to use: http://www.njstar.com/cms/

If you're using a computer where you don't have the admin privileges to add the Japanese IME, just use this website for input:

http://ajaxime.chasen.org/

After you type your text you'll need to copy and paste it were you need it. I used this a lot when using internet cafes in the US.

For mac users, you already have Japanese IME on your computer. Just go to system preference from apple mark and open Language and text, check 'Kotoeri' and that's all. You also have Japanese-English/English-Japanese dictionaries and Japanese thesaurus built in. Just open 'dictionary' application and go to preference and check those dictionaries you want to use.

Recently Google released Japanese IME for free for both Mac and Windows systems. You can download it from google website. It's much better than MS IME. For mac: http://www.google.com/intl/ja/ime/index-mac.html From here you can get Windows one as well.