Cron.php on Windows notes...
Submitted by chris on January 11, 2006 - 15:53. Drupal Configuration
As a scheduled job see:
http://drupal.org/node/31506
It appears cron.php needs to be called from a browser type request. Also try to use
your domain name when calling the cron.php script like http://YourDomain.cron.php
(versus http://YourIP/cron.php).
I actually setup a scheduled tasks in ColdFusion to load the page http://MyDomain/cron.php.