Install any version of Microsoft Word, then download this file -->Global IME for WIN98/ME
Download IE6 (Internet Explorer 6) at -->IE6
Go through the set-up, the install program will ask if you agree to Microsoft's agreement, say yes. Then the set-up will ask if you want to Typical Install, or do a Minimal/Custom Install. DO THE MINIMAL/CUSTOM install. There will be a list of different install selections, scroll down the list until you come across "Multi Language support". Select "Language Auto Selection", "Japanese Text Display Support", and "Japanese Text Input Support". If the set-up asks you to download some more components from the Internet, say yes, the set-up will download the needed files. Then all you have to do is wait.
The easiest way to install IME for these two Operating Systems is to, install Office XP, and Global IME from here --> Global IME
To our knowledge, Mac OSX(10) installs Japanese Language support automatically. Refer to your Mac OSX instruction booklet.