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I have had dual boot for a while now, having Windows 10 and Ubuntu 15.04. It was working perfectly. When I turned on the PC Grub would show up with Ubuntu and Windows 10 as options, both worked perfectly.

After messing around with Ubuntu l decided to reinstall it, so l downloaded Ubuntu 16.04, made a bootable USB and installed it over Ubuntu 15.04.

The problem is, now that I have Ubuntu 16.04 Grub won't load Windows 10, instead it displays an error as shown below.

Windows Boot Manager  

Windows failed to start. A recent hardware or software change might be the cause.  
To fix the problem:

  1. Insert your Windows installation disc and restart your computer. 
  2. Choose your language settings, and then click "Next."
  3. Click "repair your computer."

If you don't have this disc, contact your system administrator or computer
manufacturer for assistance. 

  File: \Boot\BCD  

  Status: 0xc000000a  

  Info: The Boot Configuration Data for your PC is missing or contains errors.

The curious thing is, I CAN boot Windows if I change from Legacy to UEFI or by pressing F12 (boot manager) and choosing Windows from the options.

It used to work fine and I don't know how I messed up.

karel
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Rafa Mena
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  • Why didn't you install Ubuntu with UEFI, if Windows is installed with UEFI? – dadexix86 May 29 '16 at 08:50
  • From looking at the photo, it is clear that grub is starting Microsoft's windows. However Microsoft's windows has a problem, and will not start. Microsoft checks for irrelevant hardware changes, and will refuse to start until you prove that you have an “authentic” copy, this may be your problem. – ctrl-alt-delor May 29 '16 at 09:05
  • I dont really know what UEFI and legacy are for, after installing the dualboot for the first time a saw a message saying that for a OS other than windows i should use Legacy Suport. Also, i dont know if it helps, but windows option on grub says "Windows Recovery Environment (loader) (on /dev/sda)" and it doesnt work, the one on the boot manager says "Windows Boot manager (ST1000LM024 HN-M101MBB)" – Rafa Mena May 29 '16 at 09:39
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    Possible duplicate of Installing Ubuntu on a Pre-Installed Windows with UEFI – David Foerster May 29 '16 at 16:46
  • Generally you want to have all systems installed in same boot mode. Or all UEFI if Windows is UEFI or all CSM/Legacy/BIOS if Windows is BIOS boot. UEFI and BIOS are not compatible. Once you start booting in one mode, you cannot switch. Or once you get to grub menu, you can only boot other installs in same boot mode. You should be able to dual boot from UEFI and some just use that. https://help.ubuntu.com/community/UEFI – oldfred May 29 '16 at 16:57

1 Answers1

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If you reinstall Ubuntu 16.04 as UEFI then it should sort it out.

I was used to legacy boot but finally gave UEFI a try with a newish laptop. It works fine but what I didn't realise initially, when I was trying to install Ubuntu from a USB stick, is that I had to press f12 on booting up (to offer me the 'one-time boot menu') and then select the stick under the UEFI options.

enter image description here

If I didn't do that then it just read the stick as a legacy boot stick and, if I proceeded to install it in the usual manner, then Ubuntu and the grub bootloader would be installed in 'legacy' mode.

Since Ubuntu and grub are then following the Legacy Boot rules, they don't have 'permission' to boot up a UEFI Windows partition and so you get the error.

If Ubuntu is installed in UEFI mode, then grub will be able to boot a UEFI Windows partition without any problems.

Your grub boot menu (apart from the 'extra' Ubuntu 14.04 that I've installed) will probably then look something like this:

Grub showing Windows Boot Manager

karel
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pHeLiOn
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  • Thanks a lot for the explanation!! welp i think i will resintall ubuntu to have it in UEFI as well, thanks ^^ – Rafa Mena May 29 '16 at 20:58