Note: an improved version of this video, with a far superior method is on the way. This video troubleshoots problems that can occur when System Files are preventing Secure Deletion software from wiping Folders on a Windows OS. ADDITIONAL NOTES: 1) If you use Notepad++ then you can open all the files in one go. Just highlight them in Explorer, right-click and select ‘Edit in Notepad++’. Then after you have deleted the file’s content, right click the Tab and hit close. 2) Although it is possible to change the file Properties of a group of files and uncheck the ‘Hidden’ option, you may find that individual system files may still have the ‘Hidden’ option enabled. I find this is true of the desktop.ini file and so I tend to change the properties of files individually.
Read more here:
Securely Deleting Folders Containing System Files