Engadget - How big of an upgrade is Windows 8.1? Put it this way: we just might need to review the OS all over again. Microsoft just unveiled the first major update to Windows 8, and it includes tweaks to nearly every aspect of the operating system: the lock screen, Start menu, Windows Store and onscreen keyboard. As we saw in some leaked screenshots, Microsoft also updated its native apps and added some new ones, including a stopwatch and fresh calculator. In some cases, the update even changes the way you interact with the OS. Yes, that means the Start button is back (sort of). You can now snap more than two windows into place, depending on your screen resolution, and also adjust the width of those columns so that it's not necessarily an 80 / 20 split. Additionally, Microsoft revamped the way built-in search works so that it's now more of a universal search engine, serving up apps, files, settings options and web suggestions.