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How and when to perform a Windows Registry cleanup

Desktop administrators should learn the best methods to edit the Windows registry, and how to avoid manual registry edits due to the damage that registry issues can cause.

Since the release of Windows 3.1, the Windows registry has served as a centralized database for system hardware details, user account information, application settings and more. However, decades of its evolution have brought confusion about the need for registry maintenance.

As a desktop administrator or Windows user, you should learn how the Windows registry works and review the best strategies for protecting and potentially optimizing a Windows registry.

Warning: Before you attempt a Windows registry cleanup, it's important to note that the registry is a critical part of Windows systems. Improper changes to the registry can result in system instability and other functional problems. Do not change or save any changes to a registry unless you are absolutely certain of the change.

Accessing the Windows registry

In the simplest terms, the Windows registry is a database of settings and selections. It is a huge configuration file that Windows uses to detail interactions with hardware, software and users. For example, if a user selects an application as the default program for a specific file type, such as selecting Microsoft Word to open .docx files, Windows would detail that selection in the registry so that it "remembers" the default application. The registry can hold hundreds of thousands of entries.

You can access the registry database with the native Windows Registry Editor tool. Type "regedit" into the search dialog in the Windows 10 taskbar, and then click the Registry Editor app that appears in the search results. The Windows Registry Editor will then open, allowing you to review, change or delete registry entries (Figure 1).

The Windows Registry Editor
Figure 1. The Windows Registry Editor in Windows 10 allows you to review, change, and delete registry entries.

The registry uses a nested folder structure. At the top, there are primary folders including HKEY_CURRENT_USER and HKEY_LOCAL_MACHINE. As you drill down into the folders, you'll see that each folder contains a series of keys and values. The values associated with each key can contain numbers, text or other data, such as directory paths.

For example, by expanding the HKEY_LOCAL_MACHINE folder, and then expanding the SOFTWARE folder, you can see all the installed programs registered on the Windows system. By further expanding a desired product, you can see all the keys and values for that software product (Figure 2). In most cases, there are only a few entries.

Folders in the Windows registry
Figure 2. The folders of the Windows registry with the key and value pairs in the registry.

Once you locate the desired key and value pairs, you can make changes to the entries. For example, you could right-click a key under the Name column and select Modify from the context menu. You can enter a new value for the key and click OK to save any changes. For example, you might enter a new path to the installed program (Figure 3).

Once you accept a change with the OK button, the Windows system automatically implements the change in the registry. You must restart the computer for Windows to enact the changes to the registry keys and values.

Editing the Windows registry.
Figure 3. An example of an edit you could make to the Windows registry

The big problem with this kind of process, however, is that manual changes to the registry are almost never required. Once you add key value pairs to the registry, you should generally not touch those entries. There are rare exceptions, such as correcting known damaged or incorrect entries, but this would require an understanding of precisely what needs to be changed, and what the correct entries must be. These are details that even an experienced IT administrator or user may not know.

You can close the Registry Editor by clicking File and selecting Exit, or simply clicking Close in the upper right corner of the Registry Editor dialog. The Windows system will create a copy of the registry when the system shuts down.

Dangers of running a Windows registry cleanup

The notion of a Windows registry cleanup is a legacy issue of clutter, which dates back to the early days of Windows. Older desktops' limited storage, memory and processing power might have benefited slightly from registry optimizations.

Today, the arguments for registry cleanups are simply invalid. The registry structure is more robust, and the computing resources available in even entry-level computers today make a registry cleanup unnecessary. If an entry is unneeded, the registry won't even access it, and there is no measurable performance difference between a modern computer with a cluttered or clean registry.

In order to clean a registry successfully, you must understand exactly which key and value pair entries are unneeded.

Since the registry is a database and Windows relies on the completeness and integrity of that database for proper operations, erroneous edits could cause major problems. Cleaning a Windows registry is a risky endeavor at best. Mistakes can cause serious system problems that require registry repair, and the benefits of successful cleaning are essentially insignificant. 

In order to clean a registry successfully, you must understand exactly which key and value pair entries are unneeded. This information is rarely available or ever defined precisely by Windows, leaving users and IT administrators alike to delete registry entries based on guesswork and supposition. If you remove an entry improperly, you could corrupt the registry. This would result in performance and stability problems, or even prevent Windows from starting at all.

Modern reasons for a Windows registry cleanup

Most people never need to touch the registry, and it is easy to do more harm than good. Today, a registry cleanup is typically only necessary as a means of mitigating system or application-related problems with no other fixes.

For example, consider an application that is functioning normally on the desktop. The application may be a dependency for one or more other applications on the computer. Now suppose that you update or uninstall the application, and the system experiences unexpected stability or performance problems as a consequence.

Perhaps the update changes a path or disrupts a dependency that the registry cannot reconcile. In such cases, you may consider changing or cleaning up the registry. The alternative may be to reinstall the operating system and its applications.

As another example, suppose that an uninstalled application left behind an invalid context menu entry in the registry. This issue might cause the context menu to take noticeably longer to appear in Windows Explorer when a user right-clicks on an app in the explorer. In this case, cleaning those application references from the registry might solve such problems.

Protecting and restoring the Windows registry

Given the hazards involved in editing the Windows 10 registry, it's important to preface any registry edits with a registry backup. This will allow you to be prepared if you need to restore the registry backup in the event of any corruption or damage.

Windows 10 easily creates and restores registry backups with the use of restore points. For example, you can type "create a restore point" in the search text on the Taskbar, and then select Create a restore point from the search results. In the System Protection tab, you can click Create and then follow the steps to create a restore point (Figure 4). Conversely, you can restore a restore point by returning to the System Protection tab, clicking the System Restore button, and following the steps to restore a selected restore point.

Windows registry restore point
Figure 4. You can create a restore point to back up the registry before editing.

Similarly, you can save a registry and restore the backup manually through the regedit tool by clicking File, and then selecting Export to save a copy of the registry, or Import to restore a copy of the registry.

Registry cleaning tools

You can edit the Windows 10 Registry through the native Windows 10 regedit tool. However, IT shops and power users can also select from a variety of automated Windows registry cleaning tools to assist with the process. Such tools include Wise Registry Cleaner and CCleaner. These Windows registry cleanup tools typically function by looking for content such as applications, files and folders that correspond to registry entries. If content doesn't exist to match the registry entries, the entries are deemed residual and the tool deletes them.

The primary benefits of a registry cleaning tool are speed and convenience. A tool can scan an entire system quickly and identify an array of residual registry entries that may have accumulated over time and do it far faster than a human could search. The tools typically present the results as a list, and you can select specific entries for cleaning.

But just as manual registry edits can introduce risks and problems, tools are hardly perfect. Windows registry cleanup tools have no more insight into the registry than any modest IT admin or power user, and tools also have the potential to delete entries improperly, resulting in registry damage. Registry backups are critical before attempting to use any cleaning tool as well.

Microsoft does not endorse or support the use of registry editing and cleaning tools or assume any responsibility for system problems or registry damage resulting from the use of tools. Working with a Windows registry is strictly at your own risk.

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