This contribution allows customers to download products that have been priced or discounted to zero by enabling COD payment. COD payment is normally automatically disabled for downloadable products. This enhancement requires that COD be enabled. It disables COD for any downloadable order greater than $0.00. So, if you're shipping real product, be very careful when using this modification. The change begins at line 53 of cod.php. This line could easily be modified for those shipping real & virtual product. I just didn't do it .