I had this problem for like a year, I installed a japanese language pack, it worked, but them suddenly the characters became squares, but rarely, the characters are displayed correctly.
The japanese characters are working fine on browsers, but like at the Notepad, Windows Media Player or anywhere else but the browser (Google Chrome) they are just little squares.
I've tried so much stuff to fix this that I actually gave up a long time ago but you people might help me so this is what I've tried:
1. Uninstalling and them installing.
2. Changing the region and language to Japan.
This is all I remember trying, thanks in advance.