I've installed Windows 10. It's much, much better than Windows 8. I've been using in for a few months. The other day, the Start button would not actuate. After several restarts and cold shutdowns, nothing changed. I started searching around for solutions. By the number of folks who are in the same boat as me, you'd figure Microsoft would be all over this. They can't afford another flawed OS, coming on the heels of Win 8, Vista and ME. I've had them all. And hated them all, and for different reasons. Rant over. Anyway.....after searching around I found something that worked for me. I pass it along so that it can hopefully be a solution for others. Right click task bar. Select task manager. Hit File, then Run New Task. Type powershell in the window & select create this task with administrative privileges. Type sfc /scannow. Make sure there's a space between sfc and the /. Hit enter/return. This process will take quite a few minutes. After reaching 100%, you will be advised if there were any issues. Mine didn't "find any integrity violations." I then restarted my machine, and lo and behold, the Start button was functional once again. I hope this works for you.