Let's get at it the old fashioned way. We need to remove the "Read Only" attribute from the file before we can edit it.
Open Drive C:. Do you see a file named boot? If no, click "Tools" on the toolbar and choose "Folder Options". Click on the "View" tab. Locate and remove the tick from "Hide protected operating system files" and tick the box by "Show hidden files and folders". Apply the change.
Let me know if you can see the file.