Unknowing to me Windows 10 had downloaded in the background and installed itself on my PC without even informing me. Yes, Microsoft can take over your machine without you even knowing! It appears if you have got your settings set for auto updates it will do this. Beware! Big brother is really alive! Would Microsoft like it if I came in through the back door and took over their servers and PCs, I think not!
I must admit though, there were only a couple of little hiccups which I sorted in an hour or so, everything seems to have gone over clean. It appears you can revert back to your previous operating system but only within 30 days of the install.