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Previously I had installed the Ubuntu 10.04 and Windows 7.

Now I logged on to Windows, opened the partition editor and deleted the volume containing the Ubuntu - I thought it will delete the Ubuntu and it might help me install another OS - and I restarted the system.

GRUB rescue prompt is there.

I want to log on to Windows. How can I do that?

In GRUB rescue, I tried the following:

ls
(hd0) (hd0,3) (hd0,2) (hd0,1) (hd1) (hda1,1)

Tried all combinations of ls (hdax)/, which threw out:

error: Unknown Filesystem.

I tried this: 

rootnoverify (hd0,0)
chainloader +1
makeactive
boot

It threw out:

Unknown command.

EDIT:

I installed Ubuntu from the USB. Now when I restarted the system, I got the GRUB, showing old Windows and the newly installed Ubuntu. I happily logged onto Windows. Then I used standard procedure to remove Ubuntu, so as not to have grub rescue.

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2 Answers 2

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42

You can't boot Windows from a grub rescue prompt, unless the partition with the grub modules is available. That's why you get the unknown command error. Your best solution is to reinstall the Windows bootloader. To do this boot from a Windows 7 repair CD or the Windows Installation DVD to a repair prompt and run:

bootrec /fixmbr

If you don't have a Windows repair CD or Installation DVD, it's also possible to install a Windows-like bootloader from an Ubuntu CD/USB if you have one of those:

sudo apt-get install lilo
sudo lilo -M /dev/sda mbr

Note that lilo will popup a large warning screen, but it's safe to ignore it as this refers to when it's used to boot linux.

This is what it looks like to use lilo (note the command is case-sensitive):

bcbc@neptune:~$ sudo apt-get install lilo
[sudo] password for bcbc: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Suggested packages:
  lilo-doc
The following NEW packages will be installed:
  lilo
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 275 kB of archives.
After this operation, 807 kB of additional disk space will be used.
Get:1 http://mirror.csclub.uwaterloo.ca/ubuntu/ precise/main lilo amd64 1:23.2-2 [275 kB]
Fetched 275 kB in 1s (198 kB/s)
Preconfiguring packages ...
Selecting previously unselected package lilo.
(Reading database ... 505850 files and directories currently installed.)
Unpacking lilo (from .../lilo_1%3a23.2-2_amd64.deb) ...
Processing triggers for man-db ...
Setting up lilo (1:23.2-2) ...
bcbc@neptune:~$ sudo lilo -M /dev/sda mbr
Backup copy of /dev/sda in /boot/boot.0800
The Master Boot Record of  /dev/sda  has been updated.
bcbc@neptune:~$

You'll see a warning that looks like this - it can be ignored when you use lilo as a windows-style bootloader:

enter image description here

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12
  • How do you boot from a Windows 7 install CD to a repair prompt? If I boot from the install CD, my only option is to install Windows.
    – AlxVallejo
    Jan 17, 2014 at 0:50
  • @AlxVallejo Try this: bleepingcomputer.com/tutorials/…
    – bcbc
    Jan 17, 2014 at 6:24
  • Ah, I got it. Once you hit 'Next' like you're about to install Windows, the next screen has the option to repair Windows and then enter the command prompt.
    – AlxVallejo
    Jan 17, 2014 at 15:18
  • Sorry, I have the same problem. I do not have the Windows installation DVD and I do not know why I can't boot from USB, even if I force the boot order from BIOS I still get the grub rescue prompt... What could you advise me to do?
    – user3019105
    Jul 27, 2014 at 10:22
  • 3
    Thank you man, you saved my day!!! I was able to resolve using lilo. Thanks for such a great tool!
    – user3019105
    Jul 27, 2014 at 11:30
5

If the partition holding grub files was deleted, you should be able to boot into Windows using a linux liveCd or liveUSB, using the option Boot existing OS (or Boot from Local Drive - most liveUSBs have a similar option).

E.g.: using Archlinux USB, select the option to boot an existing OS:

enter image description here

then hit Tab and point the chain-loader to the windows partition:

enter image description here

Description of comboot/chain.c32 usage on Syslinux page

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3
  • Unknown command 'chainloader'.
    – user7543
    Nov 11, 2014 at 22:39
  • 1
    @user7543 - that means you're at grub rescue prompt (the linux partition holding the grub files was probably deleted). You'll have to try my second method (via arch liveUSB) or follow bcbc instructions in the other post.
    – don_crissti
    Nov 11, 2014 at 22:44
  • The grub rescue prompt has a very limited and unique set of commands not are not at all intuitive to figure out. More details on working at the grub rescue prompt can be found here.
    – DocSalvager
    Dec 26, 2014 at 12:52

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