Hewlett-Packard, a longtime supporter of Blu-ray DVD technology for HD discs, formally joined the rival HD DVD Promotions Group this week, despite the fact that things have been shifting Blu-ray's way for the past few months in the political, psychological and technical battle for format dominance.

HP's relationship with the Sony -led Blu-ray team was recently tested, mostly unsuccessfully, when Sony refused to adopt a technology proposal from HP that it thought would make it easier for HD DVD backers to jump onto the Blu-ray bandwagon. Sony, perhaps getting a whiff of possible victory down the road, would have none of it, although Blu-ray did answer one of HP's dual requests.

Mandatory Managed Copy, which allows consumers to make legal video copies, was quickly adopted by the Blu-ray Association. However, iHD, which allows enhanced interactivity on next-gen discs (and has been earmarked for amalgamation into the still-unreleased Windows Vista from Microsoft ), was not approved by Blu-ray, and HP reportedly took offense. With such a major player now balking at solely supporting Blu-ray at this juncture, a renewed format war which appeared to be waning in recent weeks may be back for now.

Blu-ray, for its part, continues to line up significant backers. In recent days, TDK has begun shipping production samples of Blu-ray discs in write-once and RW single-sided, single layer 25GB capacity discs, and in write-once and RW single-sided, dual layer discs in 50GB capacity. TDK's discs will feature the Durabis 2 hard coating, according to a TDK statement.