wath have i do now?
Go to Configuration - Language and click on the language import utility link.
See http://docs.moodle.org/en/Category:Language for documentation pages on language issues.
Can you see "Installed language packs" on language import utility like this?
Could you check $CFG->dataroot of your config.php?
If your $CFG->dataroot is like this:
$CFG->dataroot = '/var/www/html/moodle/moodledata';
Please change it to:
$CFG->dataroot = '/var/www/moodledata';
And move moodledata directory to under /var/www.
Then try installing your language pack manually again.
I have copied the archives of the spanish package directly in the english directory.
Which version of Moodle are you using now?
If you are using Moodle 1.6 or higher, you do not need to put your spanish language pack into /lang directry as this directory is only used for English language packs (en and en_utf8). Please check Moodle documentation mentioned by Ian.
If you are using Moodle 1.5.4 or lower, please go to Administration >> Configuration >> Variables to change your default language.
Like Ivan Gutierrez Agramont I can include the language, but it can not change the language.
I use Debian 4
$CFG->dbtype = 'mysql';
$CFG->dbhost = 'localhost';
$CFG->dbname = 'moodle';
$CFG->dbuser = 'moodle';
$CFG->dbpass = 'xxxxxxxx';
$CFG->prefix = 'mdl_';
$CFG->dbpersist = "false";