‘TrustedInstaller’ is a Windows security principal that prevents you from deleting important system files, such as the contents of ‘C:\Windows’. Some of these files may grow up to several gigabytes, and you may have reasons for wanting to delete some, if you know what they do. Without permission, you’re going to have a hard time, so you’ll have to change our rights and transfer the ownership of the file/folder first.

Steps

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    Locate the protected file or folder you want to modify.
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    Right-click it and select Properties. Now switch to the Security tab.
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    Click Advanced and Change in the new window (top).
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    Type Everyone into the bottom text box and confirm using the OK button.

    • You should now be able to edit the permission entries for everyone.
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    Create a new principal with your name by clicking Add.
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    Put in your account name. Confirm the window and set everyone’s access level to Full control.
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    Confirm your changes by selecting Yes in the new window.
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    Exit the Properties menu. Then you can make the changes you want to the main file.