[support] localization

Hello. I have installed drupal successfully on a localhost running Vector Linux (similar to Slackware). I use lighttpd. I installed a British language package, specifically drupal-5.20.en-gb.po, which I put in the profiles/standard/translations directory. This seemed to work during the installation, but all words are spelled with en-US (IE, "color"). Is there something else I need to do? I tried running various things in Home » Administration » Configuration » Regional and language (IE, the Translate interface), but this did nothing. All suggestions appreciated. Mark