win 8.1 to win 10

Hi, I hope you might help me out.

I want to install win 10 over my win 8.1

D/loaded the win manager thing, and proceeded to d/load win 10.

It seems that every time I get to Windows must reboot, it doesn't and continues to install.

At the very end tells me it's going to shut down, then "Windows failed to install"

and I am back in the room 8.1.

I then d/load win 10 onto a USB flash drive, Bios, and adjust the boot sequence to boot from USB.

The same problem occurred. Kingston 480gb C drive has stacks of room.

I tried to install windows to another drive, exactly the same, my PC refuses to shut down when asked to by wins 10 installer, "I think".

Win 8.1 has been used for years, all is well, I'm not that techy, but I roughly know my way around the PC.

Can anyone help?