mysql extension won't work on vista?

hello, i just installed php5.2 on windows vista business (official release version), running through apache 2.0.59, and i can't get the mysql extension to work. i have libmysql.dll in %PHP%, %PHP% is in the system path, and php_mysql.dll in %PHP%/ext. i've even put libmysql.dll in %WINDOWS%. php.ini has extension_dir pointing to %PHP%/ext, and has extension=php_mysql.dll uncommented. restarted apache/rebooted... nothing but the error "Fatal error: Call to undefined function mysql_pconnect()" if i do something like $db = mysql_pconnect(DB_SERVER, DB_UID, DB_PWD); is there some trick to getting this to work on vista? this same setup worked fine on my XP machine. thanks, jeff