Re: help needed to boot up my system back to UNIX

[Simon Hobson]

But back to the OPs problem.
My best guess would be that the Windows system has overwritten the boot sector 
to "repair" itself. Best way to fix this is to boot into either a live CD, or 
an installer CD appropriate to the system (as long as it allows you to "break 
out" of the installer). You can then mount your system, chroot into it, and 
then repair Grub.

I'm only familiar with Debian, where current installer disks have an option to 
get into a system shell - the principle (but probably not details) will be the 
same for another distro. The steps I follow are roughly (just copied and pasted 
from another forum some time ago) :

mkdir /sysroot
mount /dev/your-root-dev /sysroot
mount /dev/your-boot-dev /sysroot/boot
mount --bind /dev /sysroot/dev
mount --bind /sys /sysroot/sys
mount --bind /proc /sysroot/proc
mount --bind /run /sysroot/run (recommended if you are using systemd)
chroot /sysroot
grub-install /dev/your-grub-boot-device (may be grub2-install on some distro)