APC Magazine reports that Microsoft has opted to disable playback of copy-protected Blu-ray and HD DVD movies in 32-bit versions of Windows Vista. The limitation is a result of support for unsigned drivers in 32-bit versions of Vista, which media companies believe could leave room for copy protection circumvention methods. 64-bit versions of the upcoming operating system will only support signed drivers and will thus retain support for the two high-definition formats.  This limitation may not upset desktop users too much; 64-bit desktop processors have been around for a while and include all AMD Athlon 64 and Athlon 64 X2 chips as well as all Intel Pentium 4 6xx, Pentium 4 5x1, Pentium D, and Core 2 Duo chips. However, Microsoft's decision will likely miff users of HD DVD- or Blu-ray-enabled notebooks like Sony's Vaio AR190G, which includes a 32-bit Intel Core Duo processor.

Update: Contrary to earlier reports, Microsoft is not cutting another Vista feature (at least not today). A Microsoft exec at TechEd Australia misspoke. Microsoft will not eliminate the ability to play HD-DVD and/or Blu-Ray content on 32-bit Vista machines. "It is up to the ISVs providing playback solutions to determine whether the intended playback environment, including environments with a 32-bit CPU, meets the performance requirements to allow high definition playback while supporting the guidelines set forth by the content owners," Microsoft said via an e-mail statement. "No version of Windows Vista will make a determination as to whether any given piece of content should play back or not. Nothing has changed regarding our policies or development plans, which we addressed at WinHEC this past May, and nothing has been 'cut.'"