Today's the day! Windows 10 is now available in 190 countries as a free upgrade to Windows 7 or 8.1 owners. Replacing an OS is no one's idea of fun, but we're actually looking forward to this one. First off, we'll be leaving behind the most hated version of Windows ever (sorry, Vista). In return, we'll get one Microsoft was so confident in that they skipped version 9 altogether because hey, Windows 10 sounds better. So how to get it? We've got a handy guide, and Microsoft has info here, but if you already reserved your free upgrade, hang in there, as Microsoft says it's rolling out in waves.