Windows 7 How do you delete windows 7 files

How do I delete Windows 7 files/folders from an old hard disk I no longer use for booting from.
I cannot delete these folders:
Program Files, Program Files(x86), ProgramData, Windows.

I get this error msg when I try to delete the above:
"You need permission to perform this action.

You require permission from TrustedInstaller to make changes to this folder"

Also I cannot delete any protected operating system files/folders, it says I need permission from the administrator. I am the administrator and there are no other user accounts on my computer.