Diskpart refusing to delete partition

[Dangerous_Dave]

I have a hard drive I'm trying to wipe but one of the partitions cannot be deleted either in disk management (windows 8.1) or diskpart. It keeps telling me that it can't delete the active boot drive or similar - but the thing is it ISN'T the active boot drive. Windows is installed and booting from my SSD. So I have no idea why it's refusing to remove the partition.

Can anyone help?

 

[Dangerous_Dave]

I'm pretty sure there weren't any boot loader files on the drive - it was just being awkward. I tried the override commands and clean etc but none of that worked. What I used in the end that did work (dredged up from a distant memory) was EaseUS partition master. That was able to get the job done finally.