On Tue, 22 Dec 2015 14:57:06 -0700, Tony Hwang
wrote:

W10 can be upgraded from W7 or W8.1(if W8, going to W8.1 is free which
is just bunch of upgrade) Then you upgrade either system to W10, if not
possible (like your box is not new enough) it will go back to where it
was saying what's the reason. Activation is based on legit product code
with W7 or W8. If you don't like W10 you can downgrade to previous
version but it has time limit, Once the limit is passed you can't downgrade.

I'm aware of this. Just reluctant jumping from Win7 to Win10. We
still have time before the free upgrade expires.