An error occurred while trying to replace the existing file DeleteFile failed code 5

C:windowsfontskhmerOS.ttf An error occurred while trying to replace the existing file; DeleteFile failed; code 5. Access is denied. during install desktop application. in this videos I got an error code 5 during install khmer unicode. my problem is I can&swith keyboard from enlish to kh. event the keyboard show me the KH icon but typing was still in English. I decide to remove reinstall khmer unicode on my desktop. after do that every thing seem to be fine.