Hey everyone. I had a 3 TB Seagate external HDD (with its own case). A short while ago the device was physically broken. So I opened the case, took out the HDD and attached it directly to my computer. But something strange happened. Windows didn't recognize the HDD and told me that I needed to format it (of course the files inside the disk were inaccessible). Well, I formatted the disk but in Windows 10 Disk Management I can only access 2 TB. I can't do anything with the remaining space (take a look at the screenshot I attached to this topic.)

Also I can't convert the disk to GPT because it's grayed out. (Again, look at the screenshot.)

How can I fully use this disk? What should I do?

I hope you dont need the data on it

seems to me that you've initialized the drive on an OS who have 2TB limitation (WIN XP ?!)
the remaining capacity is there but unallocated

Yeah and it's also a limitation of 512 sector disk with MBR partition table (basic disk) no matter what OS. Remove all partitions then convert to GPT.

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Joep - http://www.disktuna.com - video & photo repair & recovery service