how big is the hdd C is on?? If the hdd is several TB and it was full, it might take several hours to wipe and reinstall win 10.
If its a small ssd, it should be finished by now. Is there any activity showing on the PC?
If its not showing any sign of life, its probably frozen. Try restarting PC and see what happens. I expect its broken and you best of fresh installing as it will fix it and is actually just as fast as a reset. And fresh installs tend to work better than resets.
on another PC, download the
Windows 10 media creation tool and use it to make a win 10 installer on USB
After a broken reset, I would suggest a fresh install
change boot order in BIOS so USB is first, hdd second
boot from installer
follow this guide:
http://www.tenforums.com/tutorials/1950-windows-10-clean-install.html
when you reach the screen asking for licence, click "I don't have a key" and win 10 will continue to install and reactivate once finished