Question : Need to change default language.

I have the latest version of phpbb... the default language is EN_GB.  I downloaded EN-US, and uploaded it to the /phpbb/language folder.

PHPBB doesn't recognize the en-us language folder.  What have I either done wrong or have to do to make the change from en-gb to en-us?

Answer : Need to change default language.

Download the zip file
Extract the zip file with the option 'Use folder names'
Upload the resulting 'en-us' folder to your phpBB's language folder
Go to your forum's Administration Panel > System > Languages
Install the new language

You may now set it up as default language in the forum configuration, or leave the selection to your users.