Problems with installing MySQL extension on PHP5

Hi, I'm using windows with apache 1.3 web server and PHP5 installed in c:\php folder. In php.ini I put the line "extension=php_mysql.dll" extension_dir = 'c:\php\ext\' When I start Apache I receive message: "PHP startup: Unable to load dynamic library 'c:\php\ext\php_mysql.dll' - One of the library files needed to run this application cannot be found" The file 'c:\php\ext\php_mysql.dll' exist in this folder. Can someone help me ? Thanks, Rosen