Classic movie fans rejoice: One of Hollywood’s biggest movie vaults is about to be opened up. Warner Brothers has started a new DVD-on-demand service where you will eventually be able to order any of the company’s 6,800 theatrical features that are not currently available on disc. Here’s how it works: Within a week of ordering, you will receive a custom-made DVD with your requested film. The service costs approximately $20. Alternatively, customers will have the option to order films digitally for download directly