Here is the solution:
http://www.concrete5.org/help/faq/how_can_i_display_c5_in_different...

HI there,

I tried couple days to update my country's language,I did and checked the following

1.The server support gettext library
2.After successful Install the 5.4.1.1 of Concrete 5
3. I tried to update the backend language , so I download the language pack fromhttp://mygengo.com/string/p/concrete5-1....

4.I changed the config/site.php and and add the line:
define("LOCALE", 'zh_TW');

5.Upload 541.po to /concrete/languages and /concrete/languages/zh_TW/541.po (Nothing change in Backend language)

6. I also rename 541.po to messages.po and upload to /concrete/languages/zh_TW/LC_MESSAGES (Still nothing change)

Result is backend remain the same english Version, May I know which part I am doing wrong?

Thanks in Advance
Vossler

It's most likely that the language file you use isn't complete.
When parts in it are left untranslated they will appear in English on the site.

Just check it on the download site, it states there how much of it is translated.

Hey Brainakazariua,

Thanks for quickly replied, I recheck the 541.po file,it mentions it is 5.4.1RC1, But The concrete 5 I installed is 5.4.1.1, does it gonna fit the leastest language pack?

Please fill me in what shall I do? reinstall the 5.4.1? 5.4.1 (10-04-2010) - instead of 5.4.1.1 (November 19, 2010) , is that the right choice?

Try this:

1. Add define("LOCALE", 'zh_TW'); to config/site.php (which you've done.)
2. rename 541.po to messages.po
3. Upload it to

languages/zh_TW/LC_MESSAGES/messages.po

(the languages directory in the root, not in the concrete/ sub-directory.)