Let me ruin the surprise right up front by simply stating the obvious: Windows 7 is the best OS, ever, for portable computers. And I'm not just talking traditional notebooks here. I mean low-end netbooks. Tablet PCs. Touch-based tablets (and, go figure, touch-based notebooks and desktop PCs too). Ultra-Mobile PCs. Whatever. If it's even remotely identifiable as a personal computer and it can run off of battery power, you won't find a better OS than Windows 7.

Sure, Windows XP is small and lightweight, relatively speaking, but the power management is outdated and the mobile-aware functionality is wanting. And yes, Windows Vista came with improved mobile technology and better power management, but let's face it: The sudden rise of low-end netbooks caught Microsoft by surprise and Vista wasn't ready to answer that challenge. Vista's great, but it required a real computer.