My 3TB hard drive has 1TB unallocated

![Screenshot (15)|666x500](upload://i0ULRTW3Yqcq5GIYxaiQOA57QSF.png

I cannot make a new volume nor extend the previous partition. 746 GB unallocated! I think is too much to be wasted.

You probably partitioned it MBR (Master Boot Record) which has 2TB Capacity Limitation.

Re-Format and Partition it NTFS and selecting GPT (GUID Partition Table) which supports up to and greater than 2TB

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1st back up your data from the D: drive then run Diskpart.exe
type “select disk 1”
type “clean”
exit Diskpart
Open your Disk management and initialize your drive as GPT then create a partition and format

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Whenever there is "disk unknown not initialized” issue occurs, your hard drive may show unallocated space in Disk Management, and the data on which will be inaccessible or else there is another situation: there is no disk space shown in Disk Management.

There are few possible reasons behind hard disk not initialized listed below:

  1. File system corruption.
  2. Virus infection.
  3. Bad blocks and sectors.
  4. MBR damage.
  5. Connection problem.

You can give a try to below mentioned 2 different methods to resolve the issue:

Method 1. Use Disk Management to fix not initialized error on external hard drive

  1. Connect uninitialized external hard drive to your PC.
  2. Press Win + R keys, type: diskmgmt.msc and hit Enter.
  3. Find the uninitialized, unknown external hard drive with I/O device error > Right-click on it and select Initialize Disk.
  4. Then set the disk to initialize and set disk as MBR or GPT.

After this, you may reboot your PC and keep all changes. Now, your external hard drive will be recognized and read by Windows again.

Method 2. Run CMD to repair I/O device error on not initialized external hard drive

This CMD command would erase all data on the uninitialized hard drive, which you can later restore after repairing the external hard drive not initialized, with the help of any data recovery or partition recovery software:

  1. Press Win+R > Type: diskpart and hit Enter.
  2. Type: list disk and hit Enter.
  3. Type: select disk F and hit Enter; (replace F with the drive letter of an uninitialized external hard drive).
  4. Type: clean and hit Enter.
  5. Type: convert gpt or convert mbr and hit Enter.
  6. Type: create partition primary and hit Enter.
  7. Type: format quick fs=ntfs and hit Enter.
  8. Type: assign and hit Enter.
  9. Type: exit and hit Enter.

Hope it will help!

I probably did: thinking about compatibily with Windows XP. I think your advice is for a first use hard drive because I didn’t get the option to convert it to a GPT in Disk Management and I had to follow the CMD procedure. Thank you all. Everything’s fine now.