The First 15 Minutes of Millennium Racer: Y2K Fighters (Dreamcast)

Copied from SegaRetro:

Millennium Racer: Y2K Fighters is a futuristic racing game for Windows PCs. A Sega Dreamcast version was planned, but never officially announced and was cancelled for unknown reasons.

A prototype has since been found hidden on a Dreamcast Dev.Box, showing the port was fully playable.