Enter command "diskpart" and press Enter.|
Then enter "list disk" and press Enter. You will see your disks. Judging from the size of the disks, you could find which disk the eMMC is. The rest is your flash disk. Your eMMC can be disk 0 for example.
Enter “select disk 0” and press Enter. There will be "Disk 0 is now the selected disk".
Then enter "clean" and press Enter to clean the disk.
When cleaning is finished, enter the command "list disk" and press Enter to confirm whether it work. If you see the available storage is full for Disk 0, the disk is cleaned successfully.
Then enter "exit" and press Enter to leave DiskPart utility.
Then enter "startnet.cmd" command and press Enter to continue reinstalling windows.