How effective is a freeware registry cleaner at cleaning the registry on your computer?

I normally do not recommend registry cleaners. However, if you have tried everything else and your computer is still running slow then try running a registry cleaner.Also take in mind that, any Registry cleaner or other Registry utility that is poorly written and removes or changes the Registry improperly can cause issues with programs and in some situations cause Windows to stop working.However the benefit of running a registry cleaner is the removal of invalid references made in the Windows Registry pointing to a DLL, program, font, uninstalled program, or other system information that no longer exists on the computer.