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!