![](http://photos1.blogger.com/blogger/514/476/1600/Xbox360HDDVD-SysProf.jpg)
There is a separate Xbox 360 HD DVD Memory Unit listed because HD DVD players must include non-volatile memory for things such as user bookmarks, etc. On my Macs CDs and DVDs play fine using this drive, but commercial HD DVDs are not natively supported by OS X Tiger (yet).
![](http://photos1.blogger.com/blogger/514/476/400/NotReadable.jpg)
With Windows Vista on my MacBook, commercial HD DVDs are recognized (but are not playable without the correct software). The drive is recognized as a Toshiba DVD/HD X807616 USB Device. Out of interest's sake, I checked out the disc sizes of some HD DVDs. King Kong (a 188 minute movie) is 27.4 GB, but Corpse Bride is only 19 GB. The Polar Express, a reference quality 100 minute disc, is reported to be only 13 GB.