How do i format a hdd outside of windows, im in the command promp NOT in windows 10

[tony brewer]

I am working on a customers pc. It has windows 10, but corrupt. He want to put windows 7 in it. When I try to format c: it says the volumn is in use by another process. Tried force dismount but it wont let me do it.Any help?

 

[clutchc]

Let the Win7 installation pgm do that automatically.

 

[Ralston18]

DiskPart Format Override - not really sure what you have tried.....

https://technet.microsoft.com/en-us/library/cc770877(v=ws.11).aspx

What about installing the corrupt drive in another computer as a secondary drive and format it that way?

Or install it in an external USB case and reformat there?