Well, I'm not quite sure about Vista, but here's another page that describes what to do on XP:
http://greggman.com/japan/xp-ime/xp-ime.htm
You can stop after the step where you set Japanese as "Language for non-Unicode programs" and reboot, unless you'd like to install support for typing Japanese text.
Happy Holidays
,
Mion (Sonozaki Futago-tachi)