I often get this error when i'm installing mysql server and running phpmyadmin. Just in case you are also experiencing the same,
Find your php.ini file. Open your httpd.conf file and look for the PHPIniDir variable. If it is set to C:\PHP then use that ini file.
Open your php.ini file on your php folder usually at C:\PHP. Look for this line
;extension=php_mysql.dll
uncomment the line by removing the semicolon ';'
Look for the loadable extension modules directory called extension_dir, set it to
extension_dir = "c:\php\ext"
You might want to enable mbstring and curl modules as well by uncommenting the following lines on your php.ini file.
extension=php_mbstring.dll
extension=php_curl.dll
