sudo nano -w /boot/grub/grub.cfg
### BEGIN /etc/grub.d/20_memtest86+ ###
menuentry "Memory test (memtest86+)" {
insmod ext2
set root='(/dev/sda,5)'
search --no-floppy --fs-uuid --set 37a53b9e-852d-4f60-b012-f040ea22fc83
linux16 /boot/memtest86+.bin
}
menuentry "Memory test (memtest86+, serial console 115200)" {
insmod ext2
set root='(/dev/sda,5)'
search --no-floppy --fs-uuid --set 37a53b9e-852d-4f60-b012-f040ea22fc83
linux16 /boot/memtest86+.bin console=ttyS0,115200n8
}
### END /etc/grub.d/20_memtest86+ ###
### BEGIN /etc/grub.d/30_os-prober ###
menuentry "Windows XP Professional x64 Edition (on /dev/sda1)" {
insmod ntfs
set root='(/dev/sda,1)'
search --no-floppy --fs-uuid --set a6944d61944d3559
drivemap -s (hd0) ${root}
chainloader +1
}
### END /etc/grub.d/30_os-prober ###
Просто menuentry для win7 перемещаешь выше остальных и всё. Потом
sudo update-grub2