XML and Php error on windows

[hackersapien]

I know many windows users have had the same problem with php and xml.
When I try using

domxml_new_doc()

function I get this error:

[14-Oct-2003 16:45:20] PHP Fatal error:  Call to undefined function:  domxml_new_doc() in F:\webdev\php\php_xml.php on line 2

Av gone through every damn thread on the web and I cant seem to find a solution.Got any ideas post it here.

BTW am using version 4.3.3