UEFI & BIOS issues with Grub

So I’ve been doing a lot of poking around the internet and this forum to try and solve this issue. I have 3 separate hard drives on my current machine, a 250 GB SSD that contains my Windows 10 install & Windows Boot Manager, a 5TB HDD that is just bulk storage, and lastly a 1TB HDD in which is a 500 GB NTFS partition, a 500GB ext4 partition, where I installed my Manjaro, and lastly a 500MB /boot/efi FAT32 partition.

The issue I am having is that Grub is not recognizing my Windows installation, and I believe I am currently stuck with my Manjaro installation. After some research, people have mentioned that Grub will not recognize MBR and GPT, only one or the other.

My 5TB and SSD both have gpt partition tables, but the HDD that has my Manjaro installation has “msdos” partition tables (which I assume means MBR, please correct me if I’m wrong)

My question now is where do I go about fixing this? Is it safe to uninstall my Manjaro installation to restore my Windows Boot Manager? I’m not sure if that would work, and I would prefer to ask before I really make more trouble for myself. Alternatively, is there a way to fix the 1TB HDD from being on MBR to being on GPT to make my Windows Boot Manager show up in Grub?

I’m brand new to Manjaro, and never had this issue before. I’m up to try anything, and provide any terminal output to diagnose my issue.

Thank you all in advance!

There are some mobos that can boot from both methods, if your mobo can do this you can configure in your bios. In my mobo I have an option to boot from ```uefi and csm(legacy/bios)````. This way you can boot any system from bios, pulsing F8/F11 denpending machine.

Hi @static :wink:

That is bad. If grub is installed in MBR mode, so msdos means it is MBR, then it will not search for the efi partition of windows.

Yes, if you repair it with windows you will be able to boot windows.

No not possible. You need to create the gpt partition table. That means all partitions on that disk are lost then.

As @visone descibed, you need to boot the Manjaro Install Disk in UEFI mode and then install it. This way grub will find windows.

Know your system!

Know that you - unless you are very, very knowledgeable and well versed in the various methods of booting a system - should not mix EFI and MBR - those two are like fire and water - they don’t work together.