Microsoft is set to release a test version of its next Windows operating system this week, pushing ahead with a full launch that could come before the end of the year even if the depressed state of the PC market continues, Steve Ballmer, chief executive, said on Wednesday.

At the same time the software company unveiled deals with Dell and Verizon Wireless to extend the reach of its search business, nudging out arch-rival Google in two of the most closely watched alliances of their kind.