Many were surprised that Microsoft shipped their XBox 360 units before the launch of any form of high definition format, while the Playstation 3 will be released later this year with Blu-Ray capabilities. Now Microsof has announced the additional add-on drive available for the XBox 360 which will allow the playback of HD-DVD movies. The unit will be available for the holidays along with a slew of non-DVD related add-ons for the 360.