Problem with Japanese characters

Hello,

I have a site with UTF-8 encoding. The site uses some japanese characters. However some customer complains that they can see only small boxes instead of the japanese characters both with IE and Firefox.
It is probably OS related as the problem occurs only on XP machines (at least until now). But not all XP shows the wrong characters only some of them.

Any idea what to suggest to the visitors?

Thanks in advance!

Also in #HTML _↴