Drupal with chinese couldnt be installed properly

Problem:
When I was trying to install Drupal, in chinese, to my host, problems occured.
What I did was following:
1. unzip Drupal-6.13 to my host
2. unzip language pack to overwrite the original file
3. install (choosing Chinese Simplified)
Problem is like this:See picture1 (I translated the Chinese text back to English shows on the picture).
Now the site is half Chinese and half English, see picture2.

And I also installed Drupal the same way on my local computer (php5+phpmyadmin+apache+mysql), it worked fine.

Update: I tried to install Drupal (using English) first, then unzip the chinese package to overwrite original files, then go to administrator/languages/add language to add chinese-simplified, it didnt work neither, see Picture 3

Any one has a clue? Thank you very much.