Delete those damn leftover file from previous installation of Windows

I was pretty cool with the Windows 10 Preview installed on my work laptop.  When I looked closer to my system, I realized that, since I did a upgrade on an existing Windows 8.1 system, there were some system file left over.  Specifically, there's a Windows.old folder that was huge and useless in my harddisk now.

I thought, no problem.  I should be able to just drag and drop the folder in my desktop Recycle Bin.  In fact, I even changed the property  of the recycle bin so that it permanently deleted files.  It should be ultra easy, right?

Nope.

It turns out that because of the permission of a lot of these system files, I was unable to delete them.  I was like, damn it, it's my computer.  If I want to delete file, I want to delete it damn it.

So here's how I got that damn Windows.old folder deleted:

• Right click on the folder I needed to delete, and select "Properties".
• Click on "Security" tab, and then click the "Advanced ..." button.
• At the "Owner" entry, click "Change".
• Change the owner to "Everyone"
• Click the checkbox to apply such owner change to all the subfolders.
• Once completed, give "Everyone" full control.
• While you are still on the "Advanced Security Settings for xxxxx" windows, check the "Replace all child object permissions entries ...." checkbox.