CentOS更改开机启动顺序

我的电脑是win7和CentOS双系统，装系统的时候默认启动是win7。
    1. 打开终端输入  vi  /etc/grub.conf 
    2. 在 grub.conf 文件中

# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE:  You do not have a /boot partition.  This means that
#          all kernel and initrd paths are relative to /, eg.
#          root (hd0,8)
#          kernel /boot/vmlinuz-version ro root=/dev/sdb9
#          initrd /boot/initrd-[generic-]version.img
#boot=/dev/sdb
default=0
timeout=2
splashimage=(hd0,8)/boot/grub/splash.xpm.gz
hiddenmenu
title CentOS (2.6.32-358.6.2.el6.x86_64)
root (hd0,8)
kernel /boot/vmlinuz-2.6.32-358.6.2.el6.x86_64 ro root=UUID=aa9d0353-afc0-4df5-8940-5090b427c7da rd_NO_LUKS  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_MD crashkernel=auto LANG=zh_CN.UTF-8 rd_NO_LVM rd_NO_DM rhgb quiet
initrd /boot/initramfs-2.6.32-358.6.2.el6.x86_64.img
title CentOS (2.6.32-358.6.1.el6.x86_64)
root (hd0,8)
kernel /boot/vmlinuz-2.6.32-358.6.1.el6.x86_64 ro root=UUID=aa9d0353-afc0-4df5-8940-5090b427c7da rd_NO_LUKS  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_MD crashkernel=auto LANG=zh_CN.UTF-8 rd_NO_LVM rd_NO_DM rhgb quiet
initrd /boot/initramfs-2.6.32-358.6.1.el6.x86_64.img
title CentOS (2.6.32-358.el6.x86_64)
root (hd0,8)
kernel /boot/vmlinuz-2.6.32-358.el6.x86_64 ro root=UUID=aa9d0353-afc0-4df5-8940-5090b427c7da rd_NO_LUKS  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_MD crashkernel=auto LANG=zh_CN.UTF-8 rd_NO_LVM rd_NO_DM rhgb quiet
initrd /boot/initramfs-2.6.32-358.el6.x86_64.img
title win7
rootnoverify (hd0,0)
chainloader +1

default=0     //默认启动的系统 0表示第一个
timeout=2    //系统启动时选择的时间

title  //一个系统启动选项

*小提示：修改需要root权限