Change the grub boot sequence:

1. Edit grub (/etc/default/grub)

ruilin@ruilin:~$ gksudo gedit /etc/default/grub

Change: GRUB_DEFAULT=0

To: GRUB_DEFAULT="Windows 7 (loader) (on /dev/sda2)"

2. Update grub.cfg (/boot/grub/grub.cfg)

ruilin@ruilin:~$ sudo update-grub

3. Note: check the grub version:

ruilin@ruilin:~$ sudo grub-install -v

grub-install (GNU GRUB 1.97~beta4)

Reference:

GRand Unified Bootloader, version 2
(Grub 2)
https://wiki.ubuntu.com/Grub2