Google Checkout Installation help

I'm up to, "INSTALLATION NOTES" 4. Go to http://yourzencart.com/googlecheckou...nsehandler.php

I get this message:

Warning: require_once(xml-processing/gc_xmlparser.php) [function.require-once]: failed to open stream: No such file or directory in /home/content/e/n/a/enamieyes/html/store/googlecheckout/library/googleresponse.php on line 213

Fatal error: require_once() [function.require]: Failed opening required 'xml-processing/gc_xmlparser.php' (include_path='.:/usr/local/php5/lib/php:.:.') in /home/content/e/n/a/enamieyes/html/store/googlecheckout/library/googleresponse.php on line 213

Can some one please explain this in English so I can attempt to fix it?

I've searched troubleshooting and the support thread with not luck yet.

thanks.