jv16 Powertools - The only worthwhile tool for registry cleaning
I know a lot of people use CCleaner for a registry cleanup, and unfortunate people buy the ones they see in advert infested sites, but for such a risky job you should turn to the one with the most experience in this matter.
I only trust this task to jv16 Powertools, and have done since Win95 when the previous tool was called Regcleanr, which itself was inspired by Microsoft's own Regcleaner tool.
It now does much more than clean the registry and will help with clearing out the temporary crud and removing crapware.
Many tools shown in crappy adverts will promise to work miracles and speed up your PC and stop it from crashing, but you will always find that you have to pay to fix the errors it finds, by then it is too late if it is crapware and can't really help.
jv16 Powertools has different levels of aggressiveness and automation, so you can either trust it or inspect all the changes it wants to make, and manually allow each or even do it yourself now you see what the change will be.
The current Beta/Release candidate also has the ability to benchmark your connection with various DNS and set the fastest available.
Many people will argue over the usefulness of such tools, but those that say you should not do it, have generally only ever experienced the crapware tools or never done it at all.
jv16 Powertools is trialware, and you get 2 months to evaluate if you feel like buying it.
The only risk comes from using the most aggressive mode and trusting it to automatically make all the right changes. however as it comes with an undo feature you can go back to where you started (as long as windows still boots).
If you are unsure you can trust it, going back to a previous windows restart point is always an option.