Registry Mechanic is a comprehensive Registry cleaner which comes with a stack of extra features.
As usual with this kind of program, just a click or two and you can have it scan your Registry, looking for errors, orphaned references and other problems left behind by long-uninstalled programs. And in the purchased version these can also be removed with a click, although in the trial you can view the results only.
Registry Mechanic can also compact your Registry, to ensure it's consuming the absolute minimum of RAM and hard drive space.
And the program has many other features. So an "Optimize Windows" module can improve performance by applying some advanced tweaks; the "Boost your Windows Startup" module allows you to choose the programs which Windows launches when it starts; and a raft of privacy tools can delete your histories for Windows, browsers and many third-party applications, as well as securely deleting confidential files to ensure they can never be recovered.
This is all very easy to use, but if your life is already busy enough then you can set up Registry Mechanic to scan and clean up your system entirely automatically.
And don't worry about safety. Registry Mechanic hasn't reached version #11 by routinely deleting important Registry keys. But even if it makes a mistake, that's not a problem - the program records all Registry settings it deletes, so if you ever need to, then you can reverse any cleaning session in just a few seconds.