Seattle ? Microsoft Corp. will delay the consumer release of its new Windows operating system until January 2007, missing the holiday sales season and throwing some PC makers and retailers into turmoil.

The delay in Windows Vista – caused by Microsoft needing more time to enhance security and other functions – will come as a blow to Microsoft partners who were looking forward to a new operating system to boost holiday sales.

Windows Vista is Microsoft’s first major update to the company’s flagship operating system since Windows XP was released in late 2001.

The company will release some versions of the new operating system for big businesses by November as planned, but the consumer version will be postponed until January, said Jim Allchin, co-president of the Microsoft division that includes Windows.