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Intro [^]

Boot problems are probably the most feared computer problems. Without an operating system you can't access your data, get the work done or even google for help. That's why it's often a good idea to have an alternative operating system available for searching help if the main OS doesn't work. Also a copy of Clonezilla-SysRescCD can be invaluable help.

Actually, the initial reason why I (Jyrki) installed GNU/Linux at all was that I wanted to be able to fix Windows boot problems if they occur. I installed both GNU/Linux and GRUB to my external hard drive, completely separating operating systems. Even if either bootloader stopped working, I'd still be able to boot one of my OSes.

But such configuration is not easy to create, and when I installed GNU/Linux, I knew very little about it. If I didn't read the instructions I found here and there very carefully, I probably would have done a common mistake: installing GRUB to my internal hard drive. Such mistake would have caused two problems:

In this page, I simulate that situation in a virtual machine and fix both problems.

Symptoms [^]

What happens when I try to boot the external hard drive on another computer depends on the BIOS of the computer. For example, on my computer I see a Black Screen of Death when I try booting from a disk with empty Master Boot Record. Other BIOSes may boot the local operating system or display an error message (for example "Disk boot failure", "Missing operating system" or "Operating system not found").

The other problem is very easy to determine. When external drive is disconnected and I try to boot, I'll see this:

Goals [^]

Because I still want to separate my operating systems completely, I try to restore NTLDR to the Master Boot Record of the internal disk, if possible. If that's not possible, I install there another bootloader that chainloads Windows.

I could reinstall GNU/Linux completely and make sure that the GRUB is installed to the right disk this time, but it's not a good idea if I only need to overwrite the first 446 bytes (yes, bytes, not kilo- or megabytes) of the disk. So, I only install GRUB to the external disk, by using Super Grub Disk.

Your problem (if you have one at all) most likely is different, but goals are often the same.

You need to restore NTLDR if you...

You need to install GRUB if you...