I see many computers and their owners that have decided to install and run a Registry Cleaner.
If you do not know what you are doing or running then do not run a registry cleaner as they can do great damage to your system.
Playing with the registry can result in a non-booting system , the removal of key files and will it make a great difference to your computer , probably no.
Many will run the registry cleaner in the hope that their system will speed up and in all the studies I have seen the answer is probably not.
If you are that concerned about the speed of your system then format your hard drive , update and then reload your documents and software.This will give you a bigger speed bump than running a registry cleaner.
If you decide to play with your registry then you need to back it up beforehand and hope that if all else fails you will be able to restore the registry.