请教：我的grub.cfg里面的内容如下，请教怎样改代码才能让WIN7设为默认启动

#
# DO NOT EDIT THIS FILE
#
# It is automatically generated by grub-mkconfig using templates
# from /etc/grub.d and settings from /etc/default/grub
#

### BEGIN /etc/grub.d/00_header ###
if [ -s $prefix/grubenv ]; then
set have_grubenv=true
load_env
fi
set default="0"
if [ "${prev_saved_entry}" ]; then
set saved_entry="${prev_saved_entry}"
save_env saved_entry
set prev_saved_entry=
save_env prev_saved_entry
set boot_once=true
fi

function savedefault {
if [ -z "${boot_once}" ]; then
saved_entry="${chosen}"
save_env saved_entry
fi
}

function recordfail {
set recordfail=1
if [ -n "${have_grubenv}" ]; then if [ -z "${boot_once}" ]; then save_env recordfail; fi; fi
}

function load_video {
insmod vbe
insmod vga
insmod video_bochs
insmod video_cirrus
}

insmod part_msdos
insmod ext2
set root='(/dev/sda,msdos8)'
search --no-floppy --fs-uuid --set=root 446123c5-0dfe-4981-a2ac-11299deb5465
if loadfont /usr/share/grub/unicode.pf2 ; then
set gfxmode=auto
load_video
insmod gfxterm
fi
terminal_output gfxterm
insmod part_msdos
insmod ext2
set root='(/dev/sda,msdos8)'
search --no-floppy --fs-uuid --set=root 446123c5-0dfe-4981-a2ac-11299deb5465
set locale_dir=($root)/boot/grub/locale
set lang=zh_CN
insmod gettext
if [ "${recordfail}" = 1 ]; then
set timeout=-1
else
set timeout=10
fi
### END /etc/grub.d/00_header ###

### BEGIN /etc/grub.d/05_debian_theme ###
set menu_color_normal=white/black
set menu_color_highlight=black/light-gray
if background_color 44,0,30; then
clear
fi
### END /etc/grub.d/05_debian_theme ###

### BEGIN /etc/grub.d/10_linux ###
if [ ${recordfail} != 1 ]; then
if [ -e ${prefix}/gfxblacklist.txt ]; then
if hwmatch ${prefix}/gfxblacklist.txt 3; then
if [ ${match} = 0 ]; then
set linux_gfx_mode=keep
else
set linux_gfx_mode=text
fi
else
set linux_gfx_mode=text
fi
else
set linux_gfx_mode=keep
fi
else
set linux_gfx_mode=text
fi
export linux_gfx_mode
if [ "$linux_gfx_mode" != "text" ]; then load_video; fi
menuentry 'Ubuntu，Linux 2.6.38-11-generic' --class ubuntu --class gnu-linux --class gnu --class os {
recordfail
set gfxpayload=$linux_gfx_mode
insmod part_msdos
insmod ext2
set root='(/dev/sda,msdos8)'
search --no-floppy --fs-uuid --set=root 446123c5-0dfe-4981-a2ac-11299deb5465
linux /boot/vmlinuz-2.6.38-11-generic root=UUID=446123c5-0dfe-4981-a2ac-11299deb5465 ro quiet splash vt.handoff=7
initrd /boot/initrd.img-2.6.38-11-generic
}
menuentry 'Ubuntu，Linux 2.6.38-11-generic (恢复模式)' --class ubuntu --class gnu-linux --class gnu --class os {
recordfail
set gfxpayload=$linux_gfx_mode
insmod part_msdos
insmod ext2
set root='(/dev/sda,msdos8)'
search --no-floppy --fs-uuid --set=root 446123c5-0dfe-4981-a2ac-11299deb5465
echo 'Loading Linux 2.6.38-11-generic ...'
linux /boot/vmlinuz-2.6.38-11-generic root=UUID=446123c5-0dfe-4981-a2ac-11299deb5465 ro single
echo 'Loading initial ramdisk ...'
initrd /boot/initrd.img-2.6.38-11-generic
}
submenu "Previous Linux versions" {
menuentry 'Ubuntu，Linux 2.6.38-8-generic' --class ubuntu --class gnu-linux --class gnu --class os {
recordfail
set gfxpayload=$linux_gfx_mode
insmod part_msdos
insmod ext2
set root='(/dev/sda,msdos8)'
search --no-floppy --fs-uuid --set=root 446123c5-0dfe-4981-a2ac-11299deb5465
linux /boot/vmlinuz-2.6.38-8-generic root=UUID=446123c5-0dfe-4981-a2ac-11299deb5465 ro quiet splash vt.handoff=7
initrd /boot/initrd.img-2.6.38-8-generic
}
menuentry 'Ubuntu，Linux 2.6.38-8-generic (恢复模式)' --class ubuntu --class gnu-linux --class gnu --class os {
recordfail
set gfxpayload=$linux_gfx_mode
insmod part_msdos
insmod ext2
set root='(/dev/sda,msdos8)'
search --no-floppy --fs-uuid --set=root 446123c5-0dfe-4981-a2ac-11299deb5465
echo 'Loading Linux 2.6.38-8-generic ...'
linux /boot/vmlinuz-2.6.38-8-generic root=UUID=446123c5-0dfe-4981-a2ac-11299deb5465 ro single
echo 'Loading initial ramdisk ...'
initrd /boot/initrd.img-2.6.38-8-generic
}
}
### END /etc/grub.d/10_linux ###

### BEGIN /etc/grub.d/20_linux_xen ###
### END /etc/grub.d/20_linux_xen ###

### BEGIN /etc/grub.d/20_memtest86+ ###
menuentry "Memory test (memtest86+)" {
insmod part_msdos
insmod ext2
set root='(/dev/sda,msdos8)'
search --no-floppy --fs-uuid --set=root 446123c5-0dfe-4981-a2ac-11299deb5465
linux16 /boot/memtest86+.bin
}
menuentry "Memory test (memtest86+, serial console 115200)" {
insmod part_msdos
insmod ext2
set root='(/dev/sda,msdos8)'
search --no-floppy --fs-uuid --set=root 446123c5-0dfe-4981-a2ac-11299deb5465
linux16 /boot/memtest86+.bin console=ttyS0,115200n8
}
### END /etc/grub.d/20_memtest86+ ###

### BEGIN /etc/grub.d/30_os-prober ###
menuentry "Windows 7 (loader) (on /dev/sda1)" --class windows --class os {
insmod part_msdos
insmod ntfs
set root='(/dev/sda,msdos1)'
search --no-floppy --fs-uuid --set=root 60E62C6CE62C449E
chainloader +1
}
### END /etc/grub.d/30_os-prober ###

### BEGIN /etc/grub.d/40_custom ###
# This file provides an easy way to add custom menu entries. Simply type the
# menu entries you want to add after this comment. Be careful not to change
# the 'exec tail' line above.
### END /etc/grub.d/40_custom ###

### BEGIN /etc/grub.d/41_custom ###
if [ -f $prefix/custom.cfg ]; then
source $prefix/custom.cfg;
fi
### END /etc/grub.d/41_custom ###

怎样才能把多余的启动项删除？