I've got an HP Pavillion desktop running Win10. Lately (for several months) I would have problems with shutting it down. Shutting down from the start menu only killed the video output, causing my monitor to shut off. My HDD light on te PC would keep churning away indefinitely though. I would have to hold down the power button to get it to finally power off. This slowly progressed to my having to actually unplug the power cord for it to power off. Now, when I boot up I have about a 1 in 10 chance of actually getting into a working windows 10 environment. Usually I get to my desktop and cannot access the start menu or anything else. Calling up the task menu takes some time, and when I do I find that all 10 GB of my memory claims to be in use.. Trying to shut down or restart from the ctrl-alt-del screen just sends me back to having to pull the plug.
Today it took me an hour of booting and unplugging before I was able to get it to boot into safe mode. Once there I had no problems accessing software, start menu, etc. After rolling back some windows security updates I rebooted it...only to get caught in black screen limbo. I have a cursor, but nothing else. Right now it seems to be running normal, with only about 3GB of my memory used.
My video driver seems to be up to date. I have ran several different malware and spyware programs with no luck...it makes me think there may be something causing the problem during initialization during boot up.