cd /boot

安装debian下载文件

wget http://ftp.us.debian.org/debian/dists/squeeze/main/installer-amd64/current/images/netboot/debian-installer/amd64/initrd.gz

wget http://ftp.us.debian.org/debian/dists/squeeze/main/installer-amd64/current/images/netboot/debian-installer/amd64/linux

安装ubuntu下载文件

wget http://archive.ubuntu.com/ubuntu/dists/hardy/main/installer-amd64/current/images/netboot/ubuntu-installer/amd64/initrd.gz

wget http://archive.ubuntu.com/ubuntu/dists/hardy/main/installer-amd64/current/images/netboot/ubuntu-installer/amd64/linux

nano /boot/grub/grub.cfg（或者nano /boot/grub/menu.lst）
menuentry 'Install OS' {
insmod part_msdos
set root='(hd0,msdos1)'
linux /boot/linux
initrd /boot/initrd.gz
}

修改menu.lst大致也差不多

nano /boot/grub/menu.lst

在文件后面添加

title Install OS

kernel (hd0,0)/linux

initrd (hd0,0)/initrd.gz

然后重启
选择Install OS，进入安装界面，正常安装系统