Windows Vista, which hit shelves last week, is the most important version of Windows that Microsoft launches this year. But it isn't the last.Next Monday at the 3GSM wireless trade show in Barcelona, Microsoft (nasdaq: MSFT - news - people) will finally take the lid off its long-anticipated update to Windows Mobile. While Vista runs on computers and needs a ton of memory, Microsoft's cellphone operating system runs in the palm of your hand.Windows Mobile 6 isn't a huge upgrade from the current version 5, but it sports some new features aimed at both its traditional business users and mainstream...