Six years after its long-delayed but well-publicized release, Windows Vista now accounts for less than 6 percent of all Windows machines, a metrics company said earlier this month. According to Net Applications, Vista's usage share of all Windows PCs in January was 5.7 percent. That's less than a third of the share Vista enjoyed at its peak in the fall of 2009 -- about the time its successor debuted -- when it had a 20.3 percent share of all Windows machines.