The second, by a whisker, is back-compatibility.When my lovely, lovely twin-screen ex-CAD XP system was trashed by a January electric storm repeatedly cycling our power, I had to run out and buy a new PC, which came with 8.1.Took a long, hard week to sanitise 8.1's 'look & feel' from a wannabe smart-phone to something mostly useful.I also had to buy a pre-used XP office PC from Amazon (??50) as Wi