Microsoft’s Bill Mitchell wishes consumers were as excited about buying laptops as they are about buying cell phones. Unfortunately, says Mitchell, head of the company’s mobile PC efforts, there are good reasons 700 million cell phones were sold last year, compared with about 50 million laptops. Portable computers are too bulky, too slow and too quick to run out of juice. Microsoft plans to address some of these shortcomings in Longhorn, the new version of Windows that’s scheduled for release next year. To address the power issue, Microsoft is pushing laptop makers to add features such as flash memory-equipped drives, reducing the number of times a computer must spin a power-hungry hard drive.