How to Delete a System File in Windows 7 or Vista
If you need to delete or overwrite a system file in Windows 7 or Vista, you’ll quickly notice that you cannot delete system files, even as administrator. This is because Windows system files are owned by the Trusted Installer service by default, and Windows File Protection will keep them from being overwritten.
Thankfully, there’s a way that you can get around this. You need to take ownership of the files, and then assign yourself rights to delete or modify the file. For this, we’ll use the command line.
Open an administrator command prompt by typing cmd into the start menu search box, and hit the Ctrl+Shift+Enter key combination.
To take ownership of the file, you’ll need to use the takeown command.
Here’s an example:
takeown /f C:\Windows\System32\en-US\winload.exe.mui
That will give you ownership of the file, but you still have no rights to delete it. Now you can run the cacls command to give yourself full control rights to the file:
cacls C:\Windows\System32\en-US\winload.exe.mui /G username:F
Note: In username field you have to enter your username