CHICAGOScott Tarkoff, the I.T. manager for UrbaNews, LLC, slept little Monday night, plagued by visions of confused coworkers and faultily configured backup servers. "What if everything I knowfrom the optimum desktop file structure to the most secure formatting of a passwordis wrong?" Tarkoff wrote in his Linux-powered home desktop setup, which he built himself for $700. "What if the software documentation I wrote is opaque and unhelpful?" Staff at UrbaNews reported that, by Tuesday morning, Tarkoff was as condescending and cocksure as ever.