win7下安装ubuntu,引导时错选择成了ubuntu引导win7，结果开机默认进入的是ubuntu系统，怎么办？

设置WIN7为第一启动项。
在应用程序-附件-打开终端 ，运行sudo chmod +w
/boot/grub/grub.cfg然后再运行sudo gedit
/boot/grub/grub.cfg
修改顺序要 从"BEGIN"到 "END"整段移动 !
set timeout=10
------------------------------启动列表停留时间将win7的启动 begin到end 放到最前面即可
grub.cfg：引用:#
# DO NOT EDIT THIS FILE
#
# It is automatically generated by /usr/sbin/grub-mkconfig using
templates
# from /etc/grub.d and settings from /etc/default/grub
#
### BEGIN /etc/grub.d/00_header ###
if [ -s /boot/grub/grubenv ]; then
have_grubenv=true
load_env
fi
set default="0"
if [ ${prev_saved_entry} ]; then
saved_entry=${prev_saved_entry}
save_env saved_entry
prev_saved_entry=
save_env prev_saved_entry
fi
insmod ext2
set root=(hd0,9)
search --no-floppy --fs-uuid --set
0eebad35-8d15-4039-b626-3d2f97155eb7
if loadfont /usr/share/grub/unicode.pf2 ; then
set gfxmode=640x480
insmod gfxterm
insmod vbe
if terminal_output gfxterm ; then true ; else
# For backward compatibility with versions of terminal.mod that
don't
# understand terminal_output
terminal gfxterm
fi
fi
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/white
### END /etc/grub.d/05_debian_theme ###
### BEGIN /etc/grub.d/30_os-prober ### ---------------------第一启动项
menuentry "Windows 7 (loader) (on /dev/sda1)" {
insmod ntfs
set root=(hd0,1)
search --no-floppy --fs-uuid --set da0a75920a756bff
chainloader +1
}
menuentry "Windows 7 (loader) (on /dev/sda2)" {
insmod ntfs
set root=(hd0,2)
search --no-floppy --fs-uuid --set c2a2781aa27814df
chainloader +1
}
### END /etc/grub.d/30_os-prober ###
### BEGIN /etc/grub.d/10_linux ### ---------------------第二启动项
menuentry "Ubuntu, Linux 2.6.31-19-generic" {
recordfail=1
if [ -n ${have_grubenv} ]; then save_env recordfail; fi
set quiet=1
insmod ext2
set root=(hd0,8)
search --no-floppy --fs-uuid --set
8e284259-3315-4f78-8714-8e29b552cd3f
linux /vmlinuz-2.6.31-19-generic
root=UUID=0eebad35-8d15-4039-b626-3d2f97155eb7 ro quiet
splash
initrd /initrd.img-2.6.31-19-generic
}
menuentry "Ubuntu, Linux 2.6.31-19-generic (recovery mode)" {
recordfail=1
if [ -n ${have_grubenv} ]; then save_env recordfail; fi
insmod ext2
set root=(hd0,8)
search --no-floppy --fs-uuid --set
8e284259-3315-4f78-8714-8e29b552cd3f
linux /vmlinuz-2.6.31-19-generic
root=UUID=0eebad35-8d15-4039-b626-3d2f97155eb7 ro single
initrd /initrd.img-2.6.31-19-generic
}
menuentry "Ubuntu, Linux 2.6.31-14-generic" {
recordfail=1
if [ -n ${have_grubenv} ]; then save_env recordfail; fi
set quiet=1
insmod ext2
set root=(hd0,8)
search --no-floppy --fs-uuid --set
8e284259-3315-4f78-8714-8e29b552cd3f
linux /vmlinuz-2.6.31-14-generic
root=UUID=0eebad35-8d15-4039-b626-3d2f97155eb7 ro quiet
splash
initrd /initrd.img-2.6.31-14-generic
}
menuentry "Ubuntu, Linux 2.6.31-14-generic (recovery mode)" {
recordfail=1
if [ -n ${have_grubenv} ]; then save_env recordfail; fi
insmod ext2
set root=(hd0,8)
search --no-floppy --fs-uuid --set
8e284259-3315-4f78-8714-8e29b552cd3f
linux /vmlinuz-2.6.31-14-generic
root=UUID=0eebad35-8d15-4039-b626-3d2f97155eb7 ro single
initrd /initrd.img-2.6.31-14-generic
}
### END /etc/grub.d/10_linux ###
### BEGIN /etc/grub.d/20_memtest86+ ### ---------------------第三启动项
menuentry "Memory test (memtest86+)" {
linux16 /memtest86+.bin
}
menuentry "Memory test (memtest86+, serial console 115200)" {
linux16 /memtest86+.bin console=ttyS0,115200n8
}
### END /etc/grub.d/20_memtest86+ ###
### BEGIN /etc/grub.d/40_custom ### ---------------------这 些就不管了
# 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 ###

下个EasyBCD软件修改一下就可以了。
安装好EasyBCD后，运行软件，点击"Edit Boot Menu"，然后选择你要默认启动的系统就可以了。