If you have set locale to PRC as in above post, you are all set to input Chinese in Vim and Gvim. Do a ":set encoding" in vim/gvim, it should say the encoding is set to cp936 (codepage 936, ie. GBK/GB2312).
To solve these 2 problems, we need to edit our _vimrc file(located in Program Files\vim), and add these 2 lines:
set fileencoding=utf8
set fileencodings=ucs-bom,utf8,prc
The first line tell Vim to save any new file encoded in utf8, the 2nd line tell it to detect file encoding in that order.
That's it, now we can edit both utf8 and GB encoded file.
If you want to make Gvim look prettier when displaying Chinese, add following lines in _vimrc (assume you already have Chinese font installed):
if has("gui_running")
set guifont=NSimSun:h12:cGB2312
endif