For Windows XP 

 

To install Japanese input services:
Start -> Control Panel -> Regional and Language Options
Click the Languages tab
Check Install files for East Asian languages.  The languages will be
installed, and you might have to restart your computer.
Start -> Control Panel -> Regional and Language Options
Click the Languages tab
Click the Details button
Click Add 
Select Japanese as your input language and click OK
Make sure that JP Japanese -> Keyboard -> Japanese Input System (MS IME?) is
listed in the box labelled Installed Services
Click the Language Bar button
Check Show the Language bar on the desktop and Show additional Language bar
icons in the taskbar
Click all of the OK buttons to finish
 

To use Japanese in Word:
With Word open, check that you see EN in your taskbar.  Click EN and select
JP. 
Now there should be two icons next to JP: a red ball with a paintbrush and
an A. Click on A and select Hiragana
You can now write in Japanese using romaji; to convert your hiragana to
kanji as you write, while the hiragana you want to convert has a dotted
underline, press the spacebar.  To get rid of the dotted underline, press
Enter. 
 

To view Japanese emails in Hotmail using Internet Explorer:
In IE, go to View -> Encoding and select Japanese (Auto-select)