| About 300,000 of the HD DVD add-ons have been sold |
Toshiba estimated last week that about 300,000 of the add-ons had been sold.
Microsoft was one of the key backers for the HD DVD format, competing with Blu-ray, which was the format available in Sony's rival PlayStation 3 console.
Microsoft said it would continue to provide warranty support for the $130 (£115 in the UK) HD DVD add-on.
Last week, Toshiba said it would stop production of HD DVD players and recorders after major film studios decided to back Sony's Blu-ray format instead.
Toshiba said the tipping point came last month when Warner Brothers decided to release its movies only in Blu-ray.
The Xbox add-ons sold represented 30% of the one million HD DVD devices that were sold worldwide.