registry cleaners can remove duplicate files as well as unused files, icons, idle shortcuts, obsolete start menu items, temporary files and more.
But can it actually provide a dramatic difference in performance, I do not want to just run something that just provides a split second improvement whilst wasting my time.
If this cluster of obsolete registries , unused and temporary files increases , its obvious that your system will slow down ...
like if u have huge amount of unwanted cluster in your hard disk , its spinning speed will decrease.
If u want more lively example , lets take your room - if its too messy , will you like it? You surely won't .
The Windows registry is a database repository for information about a computer's configuration. The registry keep growing when you use Windows. As it does so, it attracts obsolete and unnecessary information, and gradually becomes cluttered and fragmented. With the growing of the registry, it can degrade the performance of the whole system and cause many weird software problems. To keep your computer in top performance, it is recommended to periodically clean your Windows registry with a reliable and efficient Registry Cleaner
Also check out http://askbobrankin.com/do_i_need_a_registry_cleaner.html