The DVD emulator is a feature of Development Kits. It enables a developer to create and test for DVD remastering. This means deciding witch files to store on the DVD and where on the disk to store them (layout). this is then tested using the DVD emulator software, and hardware for loading speeds and posibly potencial faults that could occur.
The Hardware required for this where a Developement kit (with the DVD emulation board) a sort of scsi cable and a XDK-Raptor card. The software was bundled with the official xdk software and a (40GB ?)Hardisk was connected to the Raptorcard where the DVD mastering image was stored on. For development it wasnt the fastest way to get an executable to the xbox, and for homebrew its pretty useless. [FIXME]