SAN FRANCISCO -- Another wave of laptop computers running on Google's Chrome operating system will be hitting stores this summer in the latest challenge to Microsoft's dominant Windows franchise.

The latest line of Chromebooks unveiled Tuesday run on a new generation of Intel microprocessors. The machines will be shipped by major personal computer makers such as Lenovo, Acer, Dell, ASUS and Toshiba. They will sell for $300 to $400.

The widening selection of Chromebooks signifies the building momentum for Google's attempt to create a compelling alternative to Windows-powered machines and Apple's Mac computers.

Intel and the PC makers embracing Chromebooks also are longtime Microsoft partners that helped make Windows so influential.

Despite the broadening support for the product, Chromebooks account for only a small fraction of PC shipments.