Edit the c:\windows\php.ini file

Change the line that reads
extension_dir="./"
to
extension_dir="c:\php\ext\"

Locate the statements
;extension=php_mysql.dll
and
;extension=php_mysqli.dll
and uncomment them by removing the semicolon (;) from the start of the lines leaving:
extension=php_mysql.dll
and
extension=php_mysqli.dll

Save the php.ini file