Cron.php on Windows notes...

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.