It's the build number. 10000 is the next build number that can be divided by 16 and 100 after 9600. That's why it's called Windows 10. X is (inofficially of course) not allowed for any non-unixoid OS. I just want to know how many apps it breaks because it has a 5-digit build number.
Looks to me as if they actually listened to the chorus of people who want a desktop experience on their desktop instead of the mess we had under W8. Honestly to me, the only thing better would be more of the customization we had under W7. One of the thing I don't like about W8 is the lack of it - the plain, flat bars and lack of an Aero type interface with customization options. I've seen some stunning desktops under W7 that you just can't get under W8. They fix that, and I'll be glad to buy W10. T