Mak, I believe the Chinese language pack adds the option to change the Vista interface to Chinese - however to view the languages it shouldn't be necessary.
I don't have it installed, but I can view chinese sites (like this one, for example: xinhua news) just fine in both IE and Opera.
Addendum:
With Windows XP, you had to manually add support (via the Regional Options dialog) for Right-to-Left languages like Arabic & Thai and for Complex Scripts like Chinese. However, Windows Vista (all versions/editions/SKUs) ships with support for the full range of Unicode and double-byte languages right out of the box for the OS and all its default apps - which, in my opinion, is one of its biggest improvements.