Had a similar error when I tried to delete an old Linux boot on one of my hard drives. The partition structure looks exactly like a standard Linux install.

TL;DR Windows will prevent you from doing it cleanly. Boot a live USB copy of Ubuntu and open up gparted. Delete the partitions from there.

The problem with the windows utility is that it is designed so some one doesn't accidentally delete their entire boot partition keeping the system from starting up. Usually this is a good thing because it is a giant pain if you do this accidentally. Even an elevated command prompt running the diskpart utility won't let you delete it. What likely happened it someone installed a Linux boot on it, decided to return it, and didn't flash the hard drive. During the Linux install, the installer flags the system partition so you know which one it is. However, Windows prevents the system partition from being delete.

However, Linux based systems usually allow significantly more user tinkering and this allow you to delete your system partition if you so choose. This allows you to boot a live copy of a Linux variant, open the respective disk utility and start zapping partitions. To accomplish this I would recommend Ubuntu and Gparted (but any other variation should be fine). The steps are as follows:

1. Create a bootable copy of Ubuntu on a USB stick or a CD.
2. Start your PC and press the boot selection key, select your USB/CD
3. Select to "try before install" or just run a live copy (can't remember the phrasing).
4. Hit the command key and open up GParted -- danger zone --
5. Find the drive that your looking to delete partitions from and start zapping. Be careful here, zapping the wrong partitions might keep Windows from starting or permanent data loss.
6. Save and apply all your changes to the drive
7. Reboot into Windows and the drive should be empty in the disk manager