While these maintenance tasks are sometimes sufficient, and are good steps to periodically perform, if you aren't cleaning your registry then you're missing a crucial step in the process.
Your registry is much like a filing cabinet for applications.
Each stores a certain amount of crucial data needed for it to function.
Yet, just as with any physical filing cabinet, your registry can develop a number of problems over time, or if managed incorrectly.
Any filing cabinet can become overfilled if not periodically cleaned, and your registry is no exception.
Sometimes application errors leave information behind that isn't correctly formatted.
Furthermore, some applications fail to clean up after themselves upon removal.
The result, over time, is a cluttered registry that is slow to access.
An application can scour the registry much more quickly than can a person search a filing cabinet, but hundreds or thousands of such lookups take time.
Eventually, this slowness will become noticeable, and if you aren't cleaning your registry then it will only get worse.
Broadly speaking, there are two ways to clean your registry.
The first is to do so manually.
You can learn about your registry's contents, what should be there and what should not.
You can also spend time learning how these items are to be formatted.
Once all this information is attained, you can work to clean your registry manually.
However, doing so is much like cleaning a business's filing cabinet on your own, without being incredibly familiar with its financial situation.
Just as throwing out important financial documents can make calculating taxes impossible, or just as disposing of certain records improperly puts businesses at legal or other risks, so does cleaning your computer's registry introduce many potential problems.
Applications may crash or lose functionality.
It's also possible to leave your computer completely unbootable, requiring a complete re-install of the operating system.
There is hope, however.
Just as you can hire an accountant or administrative assistant to help organize a business's files, so can you obtain registry cleaning software for your computer.
Such software scans your registry, knowing what data is important and which pieces can be removed.
It knows what format data should take and where it should be filed to be found by the various programs you have installed.
Registry cleaners first scan the registry and identify any changes that can safely be made.
Once they've finished this scan, they show you which pieces of information that can be safely removed and, if you approve, perform the deletion.