I did this for chinese. I just did it for japanese as well. Heres what you do:
Using the following link by Michael Kaplan, please read it before you change your continue.
Start > Run > type regedit > press enter (registry editor will open)
Expand HKEY_LOCAL_MACHINE > Expand SYSTEM > Expand CurrentControlSet > Expand Control > Expand Keyboard Layouts > Select E0010411(japanese IME) > Export a copy for backup > Double-click Layout file > type kbddv.dll in the value data box.
You may need to restart your computer. note that E0010411 is for japanese, E00E0804 is for chinese.