If you want a super-light laptop, you have to pay for it, and you have to use Windows. That’s been the (frustrating) conventional wisdom—at least until late last year, when the Taiwanese company Asus rolled out the Eee PC (pronounced as though it were a single long “e”), a two-pound, seven-inch laptop starting at a mere $300. The tradeoff: It comes with just two to eight gigabytes of flash memory instead of a conventional, larger hard drive, and a simplified Linux operating system that essentially is usable only for e-mail, Web browsing and typing.