Start menu not working, possibly reverted to Windows 8?

Hello, all.

Yesterday my start menu suddenly stopped working. In it's place I had a little white house icon on the task bar. I finally figured out that that was a Lenovo product called Pokki that was apparently designed to replace the missing start menu in Windows 8. I deleted it and rebooted but my start menu still doesn't work. Then I noticed that my C drive is now called "Windows 8_OS (C:)". Is it possible that somehow I've reverted to Windows 8 and that's why everything is messed up? I certainly did not do this deliberately. The only other thing is that I noticed that before all this started that the Comodo firewall I had been using was gone. I thought it maybe happened when I installed Windows 10 (which had been working fine for several months, BTW) - I reinstalled Comodo but then uninstalled again thinking that might be the problem. (It wasn't.)

My start menu did freeze up once before - I fixed it by deleting explorer.exe and then putting it in again as advised when I googled it. This time, I don't even have explorer.exe in my task manager.

Pokki is a third-party app, and not made by Lenovo, but it is interesting that they chose to bundle it with a computer purchase. It sounds like your current install has been corrupted, possibly by Pokki's removal. If your Windows 10 is or was activated, my best advice would be to back up your data and do a clean install of Windows 10.