Isn't GD included in PHP 5.0 ?

I tried using image functions in PHP 5.0 on my computer with Apache 2.0 installed. And I got an error message like this :
Fatal error: Call to undefined function imagecreate() in C:\Prog\SERVER\DocumentRoot\WEBSITE\test.php on line 30

Doesn't PHP 5.0 support GD library? Or is it deactivated by default? Do I have to modify PHP.ini?

If it doesn't support, how can I install GD library?

in windows you must uncomment the
;extension=php_gd2.dll
to
extension=php_gd2.dll
in Unix platforms you must compile php 5.0 with the GD library or make sure you have downloaded a package with the GD library compiled with it.

Thank you, i couldn't guess it would be so simple.