My desktop disappeared!
I've got a Lenovo Yoga ThinkPad, which I mostly use as a desktop, and sometimes use as a laptop, and rarely use as a tablet. I don't know if it's related to my Windows 10 upgrade, but last week after I flipped the computer open, it asked if I wanted to switch to tablet mode. Silly me, I clicked "yes."
The next day when I booted the machine, I had no desktop. Just the Windows 8 tiles. Ummm. Not what I wanted.
It took me a while, but I figured it out. It seems the default setting is, once you switch to Tablet Mode, that the machine will boot into whatever mode it was last in. I somehow was not doing whatever action triggers the sensor to know "get out of tablet mode" so it was just sitting like that. Other "features" of the mode are, you can't size windows -- they're either full screen, split screen, or minimized. Also, it seemed to randomly flash me back to the tile screen. Maybe that would be useful if I was actually using the machine as a tablet. Not sure.
Anyhow, here's the fix. From the Windows menu I went to Settings.
From Settings I went to System.
From System I went to Tablet Mode.
From Tablet Mode I was able to set the dropdown selection of "When I sign in ..." to say "Go to the desktop."
Problem solved. Took me a week.