Joomla 1.5 comes with UTF character set. Howver MySQL database might get installed with latin1_swedish_ci collation.

This may casue probles with displaying non latin characters, for example cyrillic.

In order to make Joomla work properly,  one needs to set in phpMyAdmin MySQL connection collation: UTF-8 Unicode (utf8)

and also to runthe following SQL query for each table:

ALTER TABLE your_table_name CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;

Do not forget to back the database if it already has data.