Hello MamaOfWill!
Perhaps the necessary language support options are not set in your computer yet. If that's the case, try going to your Control Panel's Language / Region section and make sure that your computer does have the Japanese language pack installed (typically it should come with the "East Asian Languages" option).
Kindly refer to this article for specific instructions on setting language support options for Windows XP, Vista, or 7:
http://support.brillkids.com/entries/20423062-how-to-use-little-reader-with-different-languagesOnce you have the Japanese language pack installed, LR should in turn display your Japanese lessons correctly. If that doesn't work, can you let me know which specific file you downloaded so we can check it as well?
I hope this helps!