I recently installed Arch Linux on my Windows partition via USB boot.

But GRUB still shows Windows during startup on the partition. I already tried reconfiguring the grub.cfg:

$ sudo grub-mkconfig -o /boot/grub/grub.cfg    
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-4.4.0-57-generic
Found initrd image: /boot/initrd.img-4.4.0-57-generic
Found linux image: /boot/vmlinuz-4.4.0-53-generic
Found initrd image: /boot/initrd.img-4.4.0-53-generic
Found memtest86+ image: /boot/memtest86+.elf
Found memtest86+ image: /boot/memtest86+.bin
Found Arch on /dev/sda4
Found Ubuntu 14.04.5 LTS (14.04) on /dev/sda9
done

It says it would find Arch, but during the startup there is still Windows displayed.

This is how my partitions look currently:

$ sudo parted /dev/sda print                                    
Model: ATA SAMSUNG MZ7TE256 (scsi)
Disk /dev/sda: 256GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system     Name                          Flags
 1      1049kB  1050MB  1049MB  ntfs                                          hidden, diag
 2      1050MB  1322MB  273MB   fat32           EFI system partition          boot, esp
 3      1322MB  1456MB  134MB                   Microsoft reserved partition  msftres
 4      1456MB  104GB   103GB   ext4            Basic data partition         
 9      104GB   125GB   21,0GB  ext4            Ubuntu14
 5      125GB   157GB   31,5GB  ntfs            Basic data partition          msftdata
 6      157GB   160GB   3000MB  linux-swap(v1)
 8      160GB   256GB   96,4GB  ext4
 7      256GB   256GB   128MB                                                 bios_grub

On partition 8 is Ubuntu 16, which I mainly use, and on which the GRUB files are, too.