If it is partitioned, you can remove this within the disk manager tool. Just right click on the section you wish to delete and click 'delete partition'.
If you still have no luck:
- In disk manager, identify the DISK NUMBER of he drive you want to clean
- Start > command prompt (right click and run as administrator)
- type: diskpart (press enter)
- type: list disk (press enter)
- Identify the appropriate disk number from the list that appears, this will be the number you saw in disk management (ensure this is the correct hard drive)
- type: select disk X (type in the disk number in replacement of X)
- Press Enter
- type: clean (press enter)
- type: exit (press enter)
Then the hard drive should be cleaned.