At the end of a successful full backup, the .DR file is updated with the latest hardware information about the system that is getting backed up. The hardware layout information consists of the harddisks layout and drivers. Driver files required to access the harddisks, network and and USB tape devices etc, are compressed and kept as a single DRIVER stream inside the .DR file.
When you use the Intelligent Disaster Recovery Preparation Wizard to create an IDR recovery CD image, the wizard extracts all these driver files from the .DR file onto the IDR driver database location under the media server, and makes a copy of this driver database available on the final CD image (the DRIVERS directory under the root of the CD). Also when you use the wizard to copy the .DR file to a floppy diskette, it remove the DRIVER stream out of the .DR file (due to the floppy size limitation) before the copying process, which reduces the size of the .DR file. So the .DR file that ends up on the floppy will contain all the streams except the DRIVERS stream.