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I have Ubuntu 16.04 LTS (32 bits) installed in my Laptop (Lenovo Ideapad 300) and want to make a dual boot with Windows 10. The reason is that I need to use a software (Clip Studio Paint) which only works in Windows. I know about Wine but I don't want to take risks that prevent a full functionality of the program. The partition table that I have now is MBR. I have done quite research on the Internet but did not find a specific tutorial for this. So, here is what I know, including the information received here from the previous version of the question:

  1. I could change to GPT partitioning and install Windows 10 in UEFI mode. In order to do that, without losing Ubuntu, this post may be useful (I have not tried it): How can I change/convert a Ubuntu MBR drive to a GPT, and make Ubuntu boot from EFI?

  2. I could conserve the MBR partitioning and instead install Windows 10 in BIOS mode. For that I should create the bootable media for Windows with a tool that allows to boot it in BIOS mode. The best option coud be Rufus, following @RodSmith.

Advantages of choosing UEFI installation are cited in the answer given by @RodSmith and the corresponding comments. Since I am not a tech expert, I am by now considering the other way because it spares me of some risk associated to formatting the disk.

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    "Windows 10 is not supported by MBR partition" - Incorrect. I have personally installed Win10 on an old, MBR-only system Jun 19, 2017 at 18:32
  • @AndroidDev when I tried the installation of Windows received this error message: "Windows cannot be installed to this disk. The selected disk has an MBR partition table. On EFI systems, Windows can only be installed to GPT disk." Well, now I see that the reason may be that my laptop is "EFI system"? I am sorry, I am not expert in this subjects
    – Henao
    Jun 19, 2017 at 18:38
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    It both is how drive is partitioned MBR(msdos) or gpt(GUID). And then how you boot Windows installer. How you boot install media for both Ubuntu & Windows UEFI or BIOS is how it installs. But Windows only installs to MBR with BIOS boot and only to gpt with UEFI boot. Post this from Ubuntu terminal: sudo parted -l
    – oldfred
    Jun 19, 2017 at 18:47
  • @oldfred so this means that I would need to change to UEFI after formating the partition to GPT right? But as far as I know UEFI mode does not allow to boot USB media and that's what I have to install Windows. Moreover, I actually could not do anything when tried UEFI. The screen only showed something like "checking media" (I don't remember exactly) and I had to restart with BIOS mode. The command you wrote is "sudo parted -1-" It showed me an error message. What is it for?
    – Henao
    Jun 19, 2017 at 19:08
  • copy commands, it looks like you used 1 not l (ell). Parted is a partition tool and that command shows partitions. If you have UEFI Secure boot on, you almost always have to also turn on allow USB boot. Some may require allow USB boot in all cases in UEFI settings. Older Ideapads were 32 bit UEFI only and had no BIOS boot, but were 64 bit systems. Is yours 64 bit UEFI?
    – oldfred
    Jun 19, 2017 at 19:16

1 Answer 1

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I'm afraid you're heading down a path to frustration, but it's not too late to correct course.

In Brief

If your computer is this one, it looks like it's got a 64-bit CPU and 64-bit EFI. As such, installing a 32-bit Ubuntu (apparently in BIOS/CSM/legacy mode) was a mistake. You're now trying to install (apparently 64-bit) Windows, and the Windows installer is complaining about the MBR partition table, but that's a misleading error message -- it should really be complaining about your boot mode (you've booted in EFI mode, but it needs to be in BIOS mode to be happy).

The Details

Almost all modern computers use EFI (or UEFI, which is EFI 2.x) firmware. This type of firmware replaces the much older and less capable BIOS firmware. Confusingly, many people, and even manufacturers, refer to EFI as "BIOS." This encourages applying BIOS-specific knowledge to EFIs, but doing so usually results in incorrect inferences being drawn. Adding to the confusion is the fact that most EFIs provide a feature called the Compatibility Support Module (CSM), which enables EFI-based computers to launch boot loaders and OSes designed for older BIOS (or "legacy") firmware.

One of the drawbacks to EFI is that it's difficult to boot an OS of a different bit depth than the firmware itself. That is, if you've got a 32-bit EFI, you're limited to running a 32-bit OS; and if you've got a 64-bit EFI, you're limited to running a 64-bit OS. The easiest way around this limit is to enable the CSM and install in BIOS mode. This seems to be what you've done. There are few or no real advantages to running a 32-bit OS on a 64-bit computer, though; in fact, as described by Linus Torvalds himself, 32-bit imposes significant limits once your RAM expands above 1.33 GiB. Thus, the better choice for you would have been to install a 64-bit version of Ubuntu. This would have given you better options today. As it is, you have a number of possible choices, but the two best ones are:

  • Reconfigure for 64-bit EFI-mode -- You can back up your personal data, delete the existing partitions, disable the CSM, install Windows 64-bit in EFI mode, install Ubuntu 64-bit in EFI mode, and restore your data. In the long term, this is the best solution, but of course you'll need to back up and restore your personal data, do two OS installations, and possibly deal with some hurdles concerning boot mode and the partition table.
  • Install Windows in BIOS mode -- You can boot the Windows installer in BIOS/CSM/legacy mode and install it that way. The result will be that both OSes will boot in BIOS mode, and you won't have to re-install your 32-bit Ubuntu. In the long term, though, you'll deal with the drawbacks of a 32-bit Ubuntu installation, slightly slower BIOS-mode booting, and perhaps other minor disadvantages with to this installation method. There's also a modest chance that the Windows installer will damage the partition table. (It does poorly with MBR configurations with more than four partitions.) Thus, backing up your personal data, just as in the preceding option, is highly recommended; and you may have to deal with unexpected problems.

Key to either of these options is learning how to control your boot mode. Unfortunately, details vary from one computer to another. Completely disabling the CSM is usually a reliable way to force an EFI-mode boot, but the option to do this in the firmware setup utility goes by various names, so you may end up poking around a bit to find it. If you go with a BIOS-mode Windows install, you'll need to find an option to boot the installer in BIOS mode. Typically, the computer's built-in boot manager has two options to boot external media. One option usually includes the string "UEFI" and boots in EFI mode, while the other option lacks this string and boots in BIOS mode.

Complicating this control is the fact that boot media may include BIOS-mode boot loaders, EFI-mode boot loaders, or both. If the medium lacks a given boot loader, you won't be able to boot it in that mode. Tools to convert .iso files to bootable USB flash drives can omit one or the other boot loader, even if the original .iso file has both. Thus, you may need to adjust options in whatever tool you used to create the .iso file or switch tools entirely.

For more on the CSM, see my page on the subject.

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  • I am thinking that the option of reinstalling both OS in EFI mode is better, according to your information. But my question is: is it necessary to disable the CSM for installing in EFI mode? because the USB indeed seems to be booting in EFI (when loading a live Ubuntu it shows the black screen) and I can configure the HDD to also boot in EFI. Anyway, I think that by now your response has been very enlightening, thank you.
    – Henao
    Jun 20, 2017 at 2:06
  • Most EFI-based computers have an option to leave the CSM active but enable booting in either BIOS/CSM/legacy mode or EFI/UEFI mode on a boot-by-boot basis. Completely disabling the CSM, if possible, is superior for a couple of reasons: (1) The computer often boots a little bit faster this way; and (2) With the CSM disabled, there's no chance of accidentally booting in BIOS mode. On rare occasion the CSM must be left enabled, but not used by any boot loader, because it's needed for something like an older video card without explicit EFI support. My CSM page covers this in more detail.
    – Rod Smith
    Jun 20, 2017 at 13:14
  • "Tools to convert .iso files to bootable USB flash drives can omit one or the other boot loader, even if the original .iso file has both" I realized that I cannot boot the USB in Legacy mode. After a black screen I must shut down the PC. I tried this with Ubuntu and Windows ISOs, burnt with the disk creator of Ubuntu and YUMI, respectively (in UEFI mode both work). When I look at the files stored in the USB I see efi folders and file extensions but nothing like "legacy" or "bios". Could be that the tools are omitting the BIOS bootloader? How do I know that the ISOs themselves include it?
    – Henao
    Jun 21, 2017 at 3:30
  • If you're still planning to install everything in EFI mode, then you shouldn't worry about BIOS-mode boot loaders on the installation medium; you won't use them. (They install partially invisibly, too, as raw code in the first sector of the disk.) If you've changed course and want to install Windows in BIOS mode, then I recommend you ask on a Windows forum for advice on creating a suitable Windows boot medium. Broadly speaking, though, Rufus is the most flexible tool for turning .iso files into bootable USB flash drives.
    – Rod Smith
    Jun 21, 2017 at 12:55
  • I managed to perform the installation, without changing to GPT partitioning, in the following way: 1. I created the bootable USB for Windows using YUMI, after formatting the USB to NTFS. Before that it only gave me the option to boot in UEFI mode. 2. I installed Windows 10 without major troubles. 3. I followed this post to retrieve the GRUB and be able to boot Ubuntu: help.ubuntu.com/community/Boot-Repair. Thanks for the help!
    – Henao
    Jun 28, 2017 at 21:01

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