en tu php.ini deberia poner algo asi....
;Windows Extensions
;Note that MySQL and ODBC support is now built in, so no dll is needed for it.
;
;extension=php_ftp.dll
;extension=php_bz2.dll
;extension=php_cpdf.dll
;extension=php_crack.dll
;extension=php_curl.dll
;extension=php_db.dll
extension=php_dba.dll
extension=php_dbase.dll
extension=php_dbx.dll
;extension=php_domxml.dll
;extension=php_exif.dll
;extension=php_fbsql.dll
;extension=php_fdf.dll
extension=php_filepro.dll
;extension=php_gd.dll
extension=php_gd2.dll
activa el GD o GD2, segun tu caso, y nada mas, a usarlo directamente
