Many Dell portables have the optical drive slaved to to the primary port.  In this case when your hard drive fails you have no access to the optical drive.  I think you need to replace the hard drive.  If you have files you need to get from it you can try purchasing an external drive shell that attaches to the computer via a USB port to attempt to retrieve the data.  Dells are not noted for having a lot of extra power on the USB ports so you might also need to purchase a self-powered USB hub to provide power to the drive.