(FORTUNE Magazine) – Déjà video? Sony and Toshiba have been lining up supporters for their competing high-definition next-generation DVDs in a battle over which company will own the home-video, gaming, and computer disc markets. Its like Betamax vs. VHS, only bigger. Will there be one winner? Our guide to a 21st-century format war.

WHAT TO WATCH •HP is currently with Blu-Ray but may switch sides at a big December meeting.

•Apple is also officially a Blu-Ray firm but has said its software supports both formats.

•Will Universal end up backing both formats, giving Blu-Ray access to all the big studios?

•Will Microsoft add an HD-DVD player to the Xbox in time for PlayStation's debut?

THE BOTTOM LINE Blu-Ray is the superior technology, but HD-DVD is cheaper. Sony has the most at stake--not just because it has invested more than its rivals have but because its profitable gaming and entertainment units are now linked to its struggling consumer electronics business. Neither format will probably win outright; eventually content makers may release on both formats, and hardware makers may include dual-play capability. The PlayStation and Xbox have learned to coexist profitably. Why can't Blu-Ray and HD-DVD do the same?