Solution: When CCleaner won't install (Windows) First start by reading the official documentation for solutions to install problems.     Windows 10: Do not rename the downloaded installer file, for example if it's named ccsetup561.exe leave it as is. If the installer file is renamed to something else such as CCleaner v561.exe, etc., there's a chance the installation will fail. This is specifically on Windows 10 computers.   Error opening file for writing: Screens