Former Microsoft President Rick Belluzzo, now heading the tape storage company Quantum: "Linux is clearly the biggest competitive challenge that Microsoft has ever faced. It's unlike anything before -- there's not a company behind it. It's very elusive, in a way. I don't think Linux is going to be successful as a desktop replacement. But Linux is going to surround new appliances and new segments, and really affect Microsoft through prevention of Microsoft from moving into new segments effectively."