[SOLVED] Cleaning HDD problem.

[Blazhun]

Hi all, I'm having a hard time cleaning my 1 Tb HDD. My problem is that whenever I try to clean it through command prompt I get an error saying that it can't be done due to it having boot/system files on it which might be true because I used to have this drive as my primary drive until I purchased an SSD and installed windows on that. Now apart from this problem only 800 Gb-s are usable on it another 100 Gb-s are stated as system files/boot info (I think this might be the cause of the problem). What program/method would you recommend to clean and then format this drive? I'm looking to selling this computer that's why I want to completely clean it (not NASA security lvl but something reasonable). Thank you for your answers in advance!

 

[SkyNetRising]

Make sure, you can boot from SSD with HDD disconnected.
If you clean your HDD, your system most likely will become unbootable.

Post screenshot from Disk Management.
(upload to imgur.com and post link)

 

[Blazhun]

Make sure, you can boot from SSD with HDD disconnected.
If you clean your HDD, your system most likely will become unbootable.

Post screenshot from Disk Management.
(upload to imgur.com and post link)

Thank you, managed to get it working by deleting all partitions on the HDD in Windows 10 install and after that booting back normally on the SSD then using command prompt to clean and then format the drive.