The DVD+RW Alliance announced Monday that Microsoft has become its newest member, and will join the Alliance's Executive and Steering Committee. Microsoft previously committed to supporting the DVD+R and DVD+RW rewriteable DVD format in Longhorn, the next Windows version, last April during the WinHEC 2002 trade show, but company executives told me at the time that Microsoft would support other recordable DVD formats as well, including DVD-R and DVD-RW. It's unclear at this time whether this week's announcement means that Microsoft and its future products will now only natively support DVD+R and DVD+RW.

"In an effort to evaluate providing support for writable DVD and other digital media formats, Microsoft has decided to join the DVD+RW Alliance as a core member," said Tom Phillips, the general manager of the Windows Hardware Experience Group at Microsoft. "Microsoft is committed to the convergence and compatibility in both PC and consumer electronics applications.  Microsoft is happy to become a part of the DVD+RW Alliance and help promote writable DVD standards that are aligned with the Mt. Rainier technology."

Despite Microsoft's backing, DVD+RW is currently losing the compatibility and sales war to competing formats such as DVD-R and DVD-RW, which are supported by the DVD Forum, backed by Apple, Hitachi, NEC, Pioneer, Ricoh, Sony, Thomson, and Yamaha. The DVD+RW Alliance, which supports DVD+R and DVD+RW formats, is backed by Dell, Hewlett-Packard, MCC/Verbatim, Philips, Microsoft, Ricoh, Sony, Thomson and Yamaha. Given that several companies support both formats, its not inconceivable that Microsoft will also through its backing behind the DVD Forum. Currently, incompatibilities between the formats are slowing adoption.