I don't know much other then Microsoft supports the HD-DVD and Sony the Blu-ray. If you ask me Microsoft was stupid when they didn't just let the xbox 360 play the HD-DVD's without an add on, it would've propelled HD-DVD sales if it came with it regularly considering how much earlier it was released compared with Sony. If you take a look at stats once the PS3 went on sale blu-ray sales rose tremendously.
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