My laptop (Lenovo v470) has a pre-installed Windows 7, but it doesn't start up and also startup repair doesn't work (missingosloader error). I want to re-install Windows 7 but all partitions are MBR and boot mode is UEFI and I get the error

Windows cannot be installed on this disk. The selected disk has an MBR partition table. On EFI systems, Windows can only installed on GPT disks."

I don't want to lose my data and I know there are approaches to change MBR to GPT without losing data but I don't want to take that risk. So I decided to change boot mode to Legacy. Unfortunately, in bios setup > boot menu, there is no boot mode option to change (not even disabled option). I can just change bootable media priority.

Is there any way to change boot mode through Ubuntu live or recovery command prompt?

Edit: Boot Menu that doesn't have boot mode. Boot Menu

Configuration tab Configuration Menu

Information tab BIOS information tab

Security tab BIOS security tab

Exit tab BIOS exit tab

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    Since you're considering the use of a live session then do your backup bfrom it and then use Gparted to create a new - GPT - partition table (all partitions will be deleted). Now you can install in the preferred UEFI mode. – GabrielaGarcia Oct 1 at 15:34
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    "all partitions are MBR and boot mode is UEFI and get the error" Then how was W7 installed in the first place? This makes no sense. – Moab Oct 1 at 15:44
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    The error is indicating you have enabled UEFI mode, and the boot environment has detected this fact, which means you can only install Windows on a GPT parttiion. Since your HDD contains MBR partition, which means Legacy mode was enabled when Windows was installed, you should enable Legacy mode in order to boot into Windows. The reason you are unable to boot into Windows is due to the fact, Legacy mode has been disabled, which likely is the entire reason you want to reinstall it? At this point I would transfer your data off the HDD and reformat the HDD so you have a GPT partition. – Ramhound Oct 1 at 17:13
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    It is not possible to install Windows, while in UEFI mode, on a MBR partition. So you can either, convert the disk to GPT, or enable Legacy mode and install Windows. "is possible that my product key (OEM key) will be invalid by formatting the disk. Is it normal that I can't choose boot mode?" - Windows 7 are never made invalid. There is always a solution that can be performed to activate Windows 7 with a legitmant license key. All OEM license keys purchased from a legitmant retailer are legitmant. – Ramhound Oct 1 at 17:14
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    @Vahid - All I know the option to enable/disable UEFI mode has to be there, because it's currently enabled, yet you have a disk which had I presume a working Windows 7 installation on a MBR partition. However, I don't know that for certain, since you have only indicated it currently does not work (which would make sense if Legacy mode was disabled). – Ramhound Oct 1 at 20:42

To sum up the discussions in the comments, I should use Linux Live USB/CD to backup my files and then convert MBR disk to GPT (there are lots of tutorials for that with and without losing data). For others that have the same issue, I suggest to consider F9 (Setup Defaults in the BIOS) and updating firmware as potential solutions (need to be investigated well). At the moment, I want to do backup and then MBT to GPT conversion.

  • I would never want to do some weird attempt to save my data during reformat. Use "GParted" from a Linux USB and reformat to GPT which would cause a full data wipe, then restore, but I'm OCD. From what I read you are correct, it is possible to convert without data loss! (Learn something on this site every day) – FreeSoftwareServers Oct 4 at 12:59

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