系统首先安装了Ubuntu ，然后安装window系统，如果不做任何改动，那么将无法启动window。不过不用担心，可以采用下面进行修改。（红色标记为修改的内容）.

升级以后，因为内核版本会更新，但以前的内核版本Ubuntu ，对于已 不再需要返回的启动项， 如果每次开机都出现这么一长串的话，严重影响心情，可通过下述操作为 menu.lst减肥

1. 启动终端，在终端里面输入命令行： sudo vim /boot/grub/menu.lst ,回车后输入你的系统管理员密码

   这时弹出会在文本编辑器里面打开一个menu.lst文件,以下是我的部分menu.lst默认启动OS为XP系统，每次系统启动后自动从XP开始启动；

# menu.lst - See: grub(8), info grub, update-grub(8)

#            grub-install(8), grub-floppy(8),

#            grub-md5-crypt, /usr/share/doc/grub

#            and /usr/share/doc/grub-doc/.

## default num

# Set the default entry to the entry number NUM. Numbering starts from 0, and

# the entry number 0 is the default if the command is not used.

#

# You can specify 'saved' instead of a number. In this case, the default entry

# is the entry saved with the command 'savedefault'.

# WARNING: If you are using dmraid do not use 'savedefault' or your

# array will desync and will not let you boot your system.

default        3

## timeout sec

# Set a timeout, in SEC seconds, before automatically booting the default entry

# (normally the first entry defined).

timeout        10

## hiddenmenu

# Hides the menu by default (press ESC to see the menu)

#hiddenmenu

#Remark the  hiddenmenu，or the menulist will not display,

# Pretty colours

#color cyan/blue white/blue

## password ['--md5'] passwd

# If used in the first section of a menu file, disable all interactive editing

# control (menu entry editor and command-line)  and entries protected by the

# command 'lock'

# e.g. password topsecret

#      password --md5 $1$gLhU0/$aW78kHK1QfV3P2b2znUoe/

# password topsecret

#

# examples

#

# title        Windows 95/98/NT/2000

# root        (hd0,0)

# makeactive

# chainloader    +1

#

# title        Linux

# root        (hd0,1)

# kernel    /vmlinuz root=/dev/hda2 ro

#

# Put static boot stanzas before and/or after AUTOMAGIC KERNEL LIST

### BEGIN AUTOMAGIC KERNELS LIST

## lines between the AUTOMAGIC KERNELS LIST markers will be modified

## by the debian update-grub script except for the default options below

## DO NOT UNCOMMENT THEM, Just edit them to your needs

## ## Start Default Options ##

## default kernel options

## default kernel options for automagic boot options

## If you want special options for specific kernels use kopt_x_y_z

## where x.y.z is kernel version. Minor versions can be omitted.

## e.g. kopt=root=/dev/hda1 ro

##      kopt_2_6_8=root=/dev/hdc1 ro

##      kopt_2_6_8_2_686=root=/dev/hdc2 ro

# kopt=root=UUID=ca95a4f5-ff60-41b0-9332-d1d60c93ffda ro

## default grub root device

## e.g. groot=(hd0,0)

# groot=ca95a4f5-ff60-41b0-9332-d1d60c93ffda

## should update-grub create alternative automagic boot options

## e.g. alternative=true

##      alternative=false

# alternative=true

## should update-grub lock alternative automagic boot options

## e.g. lockalternative=true

##      lockalternative=false

# lockalternative=false

## additional options to use with the default boot option, but not with the

## alternatives

## e.g. defoptions=vga=791 resume=/dev/hda5

# defoptions=quiet splash

## should update-grub lock old automagic boot options

## e.g. lockold=false

##      lockold=true

# lockold=false

## Xen hypervisor options to use with the default Xen boot option

# xenhopt=

## Xen Linux kernel options to use with the default Xen boot option

# xenkopt=console=tty0

## altoption boot targets option

## multiple altoptions lines are allowed

## e.g. altoptions=(extra menu suffix) extra boot options

##      altoptions=(recovery) single

# altoptions=(recovery mode) single

## controls how many kernels should be put into the menu.lst

## only counts the first occurence of a kernel, not the

## alternative kernel options

## e.g. howmany=all

##      howmany=7

# howmany=all

## specify if running in Xen domU or have grub detect automatically

## update-grub will ignore non-xen kernels when running in domU and vice versa

## e.g. indomU=detect

##      indomU=true

##      indomU=false

# indomU=detect

## should update-grub create memtest86 boot option

## e.g. memtest86=true

##      memtest86=false

# memtest86=true

## should update-grub adjust the value of the default booted system

## can be true or false

# updatedefaultentry=false

## should update-grub add savedefault to the default options

## can be true or false

# savedefault=false

## ## End Default Options ##

title        Ubuntu 9.04, kernel 2.6.28-18-generic

uuid        ca95a4f5-ff60-41b0-9332-d1d60c93ffda

kernel        /boot/vmlinuz-2.6.28-18-generic root=UUID=ca95a4f5-ff60-41b0-9332-d1d60c93ffda ro quiet splash

initrd        /boot/initrd.img-2.6.28-18-generic

quiet

### END DEBIAN AUTOMAGIC KERNELS LIST

 #Add the below context ,because the os which my pc  is window xp,so the parameter is

#title        Microsoft Windows XP Professional ,if your os is other ,you may modify accordin to the os .

# This is a divider, added to separate the menu items below from the Debian

# ones.

title        Other operating systems:

root

# This entry automatically added by the Debian installer for a non-linux OS

# on /dev/sda1

title        Microsoft Windows XP Professional

rootnoverify    (hd0,0)

savedefault

makeactive

chainloader    +1