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I had a Windows 7 and Ubuntu dual boot system, after upgrading to Windows 8 I uninstalled Ubuntu (deleted partition) and was getting a 'grub: no such partition' error.

I tried fixing by re-installing Ubuntu and also using Windows 8 USB using bootrec everything.

Now I am just getting a blank screen with cursor (_) when I boot up.

I just want to get back the ability to boot into Windows 8.

Edit: Can not install Windows 8 again as it requires reboot, which leads to the blank screen again.

Other partitions seems good, except the Ubuntu one I deleted, swap and a windows ~350 MB partition which I think was as Ubuntu boot when I tried to re-install (not sure).

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Probably, while removing Ubuntu, you inadvertently removed Win8 as well. Try using another bootloader disk to get into the machine and find out what is retained or present on the disk. –  Mamta Dalal Nov 1 '12 at 9:03
    
I checked, only the ubuntu partition and swap were deleted. There is another about 350mb windows partition which seems to be overwritten. –  spexy Nov 1 '12 at 14:09
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3 Answers

up vote 1 down vote accepted

[FIXED] Recovered Windows 7 and now re-upgrading to 8. Had to format the windows partition.

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Accept this as your answer so that future seekers of similar question may find the answer –  Mamta Dalal Nov 2 '12 at 9:40
    
It asks me to accept it after 15 hours. Will do. –  spexy Nov 2 '12 at 14:51
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If you need to restore the Windows boot loader after using GRUB (or something similar) and subsequently deleting its installation, you can use the Windows setup disk. The following refers to the Windows 7 installation media, but Windows 8 should have similar options from the disc.

Boot onto the disk and click the "Repair your computer" on the install screen that eventually comes up. If the only problem is the bootloader, it should automatically detect this and restore it.

If you are running an earlier version of Windows, or it doesn't (for whatever reason) automatically restore the bootloader, you'll have to do it manually.

Boot to the CD again and go through the prompts to get you to the "Recovery console". From here, enter the following command:

bootrec /rebuildbcd

This will reinstall the Windows bootloader for you, automatically detecting the location of your Windows installation.

Once it completes, restart your computer, and you should see Windows again.

However, if these steps don't resolve the issue, you might have to dig deeper. Note: additional info is taken from Microsoft KB927392.

  1. You can rebuild the bootloader completely if necessary, by exporting and then deleting the existing bcd, and then doing the rebuild step, again. In the recovery console, type:

    bcdedit /export C:\BCD_Backup
    c:
    cd boot
    attrib bcd -s -h -r
    ren c:\boot\bcd bcd.old
    bootrec /RebuildBcd
    
  2. If the OS doesn't get detected, you can try using bootrec /scanos to have it list all operating systems on all disks compatible with the bootloader, including those not in the BCD store.

  3. Using bootrec /fixmbr will rewrite the Master Boot Record to the system partition. This might be useful if it becomes corrupted.

  4. Using bootrec /fixboot will write a new boot sector. This might be important if it was replaced with a nonstandard boot sector, was damaged, or an older version of Windows (before Vista and 7) was installed alongside the newer version.

When doing these operations, it's important to note that you're changing core elements of your system disk. Always make sure your data is backed up to a separate disk before doing anything that might potentially cause data loss. These steps won't necessarily cause you to lose your data, but prudence is always important. As they say: "Hope for the best and prepare for the worst."

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Did try this, returned no OS detected(not the exact message) –  spexy Nov 1 '12 at 16:35
    
I'll add additional info. I don't know what you tried, but there are other things that are available before you'd need to resort to reinstalling. –  Ben Richards Nov 1 '12 at 16:44
    
I realize that in an attempt to keep the question short I excluded some details :( /Scanos and /RebuildBcd returned no OS. –  spexy Nov 1 '12 at 17:10
    
@spexygeek It's always best to include as much information as possible so that we can help you better and not waste time suggesting things you've already tried. But thanks for the clarification. –  Ben Richards Nov 1 '12 at 17:10
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I experienced this issue as well. I found that I can use CTRL + ALT + DEL at the black screen. This allows me to start the Task Manager. Within the Task Manager select New Task (RUN) from the File menu. Type CMD and select the check box to run this command as an administrator. Within the command prompt, type sfc/scannow and let it scan your system. Once completed, reboot the machine by pressing CTRL + ALT + DEL again and select restart from the Power button on the bottom right.

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