How to format the C drive to reinstall the Win10 system?

Normal channel upgrade Win10/Win8.1 Win10 will not format the C drive, so the installed Win10 system will not be clean, there are files in the C drive that retain the original system. So how to format the C drive and reinstall the system?

Format C drive
Specific method:
1, download Win10 ISO image; (Download address: Win10 system ISO image)
2, making U disk boot; (refer to: use U disk to make Win10 system disk tutorial)
3, start pe format C drive;
4, install win10 in pe.
The above is how to format the C disk reinstallation system, using the traditional reinstallation system, you can automatically format the C drive, which is also the most pure Win10 system installed.