Make sure that the drive is attached to your PC and powered on. In other words, make sure that your system recognizes your external drive.

Next "Right Click" on your "My Computer" icon and choose "Manage" from the drop down menu. This will open the Management Console. Next, click on "Disk Management" which will be located near the bottom of the left pane of the management console. When the disk management console appears find the external drive in the drive listing and click on it. The partition will become
highlighted in blue to indicate that it is selected. You can then right click on it and select "delete partition" from the menu that opens up. You can also create a new partition the same way if you'd like.

Good luck,

Sources: http://noblepassmercy..com/2015/03/how-to-remove-partition-from-external.html

More like shrinking the partition.

Plz help

I removed an hard disk from my old system and want to use it in my new system as external disk, but it is showing 4 partitions. Although i can access all those files but I want to remove other partitions (system, recovery and hp tools). Please how do i go about it?

Sogaz:
Plz help

I removed an hard disk from my old system and want to use it in my new system as external disk, but it is showing 4 partitions. Although i can access all those files but I want to remove other partitions (system, recovery and hp tools). Please how do i go about it?

Use the method the op stated above or simply format