Just been having major problems with 10. After loading it at launch the stupid thing claimed that it couldn't find the start menu and cortana and said that it would try to find them next time I logged in, offering one option - to log out - and so a frustrating loop began, cos it still couldn't find the missing bits. Knowledgeable friend eventually took my machine back to factory setting. 10 was then reinstalled using a disc rather than download which worked for a couple of months, then the same problem reoccured and the disc reload wouldn't work. 45 minutes on the Microsft chat facilty achieved nothing. A similar amount of time on the helpline ended with the machine worse than before. Microsoft did offer a paying subscription to sort it out!
I have ended up doing another factory reset followed by all the nause of reloading software, favourites etc. Microsoft then emailed me for feedback. I normally can't be bothered, but this time I did telling them what I really thought of their "service" and that my next computer would be a Mac. I only bought this machine in April and it has been temperamental from the outset. Had I known then what I know now I would have gone for the Mac.
I am now back using 8 until I pluck up the courage to go for 10 again.
I am a man of simple tastes, I am quite satisfied with the best. (Oscar Wilde)