Windows doesn't have sudo (not yet, at least) and privileges work a bit different as even as an administrator, you may not have full rights.

To overcome that obstacle, you'd need to run a shell as an administrator (hold CTRL+Shift, then use the start menu entry or right-click it and select run as administrator).

Next obstacle: We have a separate drive for each partition, but no root folder.

If we assume we're running on a laptop or PC with a single drive and a single partition*, then it's just

In cmd.exe:

del /F /S C:\

In Powershell:

Remove-Item -Recurse -Force -Path C:\

When you want to delete all (mounted) partitions/drives, you need to iterate over them. (Note that's from the top of my head, didn't check the script if it works).

In cmd.exe:

REM Not gonna do that, I'm no masochist

In Powershell:

Get-PSDrive -PSProvider FileSystem | Foreach-Object {
    Remove-Item -Recurse -Force -Path "$($_.Name):\"
}

Done. Mounting additional partitions before that is left as an exercise for the reader.

*note that even a standard installation of windows creates 3 partitions. One for the bootloader, one for the recovery system and then the system drive. Only the latter is mounted and will be deleted by this. The other two will still be intact.