I'll assume you are using Windows XP.
Go to the Control Panel (activate classic view)>Regional and
Language Options>Languages. Check the box for "Install files for
East Asian Languages", and a prompt will ask you to insert your
WinXP Installation CD. Do likewise and font + decoder files for
Chinese, Japanese, Korean etc. will be installed.
Once the update is complete, a language bar will appear at the
bottom of your screen. You can add new languages for input via the
options menu.
I hope that helped.