Mid 2014 IMAC with orginal Partion only being 400gb.

Question

I have a 1tb hardrive how can I restore the hard drive to factory settings and just have 1 partion at 1tb?
I have gone through the disk utility and just have 1 partition at 1tb but it wont let me. 

Answer 1

Hi DevilDoc123,
It sounds like you have 2 partitions of which you want to delete one, and enlarge the other to regain all the space under a single partition. You will need to delete the second partition first, then you will be able to resize the other. These steps from the Disk Utility Help should assist you in that:
Partition a disk - Disk Utility Help
To enlarge a partition, you must delete the partition that comes after it on the disk, then move the end point of the partition you want to enlarge into the freed space. You can’t enlarge the last partition on a disk.
WARNING: When you delete a partition, all data on it is erased. Be sure to back up your disk's databefore you begin.
Select the disk in the sidebar that contains the partition you want to enlarge, then click Partition.
In the Partition Layout list, select the partition beneath the partition you want to enlarge, then click Delete .
The partition is immediately erased, leaving the space it formerly occupied available.
Resize the partition by doing one of the following:
Drag the dividers between the partitions in the Partition Layout list.
Select a partition in the Partition Layout list, then enter a value in the Size field.
Click Apply.
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All the very best,
Sterling