CCleaner Issue causes Start not to work.

[Rayden]

I have just installed CCleaner and run it to clean up my system.  That all seemed to work. Now, when I try to run Command Prompt as administrator, nothing happens.  Also the start button now does not work.  I fortunately made a restore point before making the changes, and I think I've now managed to get the system working again.  However, using CCleaner now seems rathre dangerous or maybe I've misused it.   Can you please advise how I avoid such disasters?

[nukecad]

Firstly, good to hear you got your system working again.

I suspect that you used the Registry Cleaner?

Registry Cleaning is a specialist tool used to help when fixing an already 'broken' computer, if used on a fully working computer it can sometimes do the opposite and 'break' things.

You should not use a Registry Cleaner as a general cleaning tool - You should especially not use it with Windows 10.
Windows 10 changes things in the registry too often for any Reg Cleaner to keep up.

Some get away with using it regularly, some 'break' their machines and have to restore as you did, in some cases they have to reinstall Windows altogether.

I think that what may have happened here is the Windows Patch Tuesday Update this week, has changed something in the registry.
As CCleaner v5.70 was released last week, before Patch Tuesday, then it won't/can't know about any changes Windows has made to the registry since.
So a Registry Clean may have removed a new/changed registry entry that CCleaner didn't recognise as needed but that Windows now needs on your machine.

Here is what Microsoft have to say about using a Registry Cleaner on a regular basis - ie. Don't do it.
https://support.microsoft.com/en-gb/help/2563254/microsoft-support-policy-for-the-use-of-registry-cleaning-utilities

PS. The usual next question is why does the Registry Cleaner have such a big button in CCleaner then?
It's simply a hangover from earlier days, when older Windows versions may have benefited from a registry clean.
We have been promised for a while that the Reg Cleaner in CCleaner will be made less prominent by moving it into the 'Tools' so that people are less tempted to use it without thinking/knowing what Reg Cleaning should be used for. (Some would prefer if it was removed altogether).

[Rayden]

Thank you very much for your detailed reply.  You are completely correct, that is what I did, and I was indeed fearful that I would have to reinstall WIndows.  I will resist using register editor.  Having said that though, there did seem to be an enormous amount of junk there presumably from apps etc that I've deleted etc. However, i suppose that its not doing any harm, apart from taking up a bit of space.  Once again thank you.

[nukecad]

Unused and left over registry entries will only take up a few KB of space at most, with the size of modern dirves that's nothing and gaining a few extra KB isn't really needed.

Getting rid of them, whilst nice and neat, isn't going to affect (speed up) your computer in any way.

The only ones that could realy be a problem is if some virus/malware/spyware/adware/etc. put something in the registry.
TBH your AntiVirus/AntiMalware app should prevent that in most cases.
But if your particular AV/AM didn't catch the infection then that may be the time to use a registry cleaner (used carefully).
Hence what I said above about registry cleaning being a tool to help trying to fix an already 'broken' computer.

Some, many, apps don't fully uninstall with the standard uninstaller.
That's where an uninstaller app like Revo can help, it can find and remove leftover files, folders, and reg entries that  the standard uninstall left behind.
Like anything else that can modify the registry use it carefully, and use the 'make a restore point' option, but it does lead you through it if your read what it tells you at each stage.
There is a free version, or a Pro version with a trial. https://www.revouninstaller.com/revo-uninstaller-free-download/
With Pro, or the Pro trial, 'Forced Uninstall' lets you use their log database to remove leftovers of stuff you had installed/uninstalled before you even got Revo.