Class 'Zend_Exception' not found (no replies)

I've just copied the latest Piwik folder to a new 'analytics' folder in my webserver hosted by IIS on Windows 2008 Server. I tried going to http://www.mydomain.com/analytics/piwik/index.php to start the installation after creating a MySQL database and user, where I was told I needed to execute some 'cacls' commands. I started with the first 'tmp' directory it requested, then refreshed the index.php page and have been given this error:


Fatal error: Class 'Zend_Exception' not found in C:\inetpub\wwwroot\analytics\piwik\libs\Zend\Exception.php on line 39


I cannot seem to continue with the installation since I continually get this error when trying to go to this page.

Help??