Windows 10: Installation problem, 4TB HDD in W10 Home

Hi,

I've just tried to install a brand new 4TB Seagate HDD in an external caddy connected via a USB3 cable to my W10 Home PC. Nothing occurred when I connected it, but I found it in Disk Management. Accessing it in DM required me to initiate the disk and it offered me two choices: one commencing with G (the default), the other commencing with M (I'm sorry, but I don't remember them exactly enough).

I chose the M option, thinking that I might want to connect to an older version of Windows sometime, but in hindsight I think this is rather unlikely and would like to reverse this - I suppose it's too late now (some low-level format, perhaps?) to change it to the G option.

What I'm left with is 2 partitions, one of which I can set up as a simple volume and format it. The other partition (~1.6TB) is inaccessible. Right-clicking this partition gives me only Help and Properties. I'd prefer to merge both partitions, but if I've got to live with both, then I'd like also to be able to make it a simple volume too.

Is this do-able?

Thanks in advance,
Paul.

It seems like the HDD is just a second HDD for data storage? You will have to wipe the disk to convert it to GPT easily, here's how:

Change a Master Boot Record Disk into a GUID Partition Table Disk

As long as you are only using the 4 TB drive as a second drive for data storage, you want it to be GPT. It does not matter if the computer is Legacy BIOS or UEFI.

Thank you both for your very valuable advice. I've successfully reinstated the ~4TB partition and formatted it. I'm in the process of moving a good number of files to it as I type.

Yes, the disk is intended as a data storage unit, only.

Many thanks. I'm marking this thread as solved because of your input.

Paul.