Registry Clean Pro

A utility to fix errors and optimize the performance of the Windows registry.

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Registry Clean Pro: Technical Details

Registry Clean Pro locates and fixes errors in the following registry sections:

  • Startup.
  • Shared DLLs.
  • Fonts.
  • Application Info.
  • COM/ActiveX.
  • File Extensions.
  • Shared Folders.
  • Help Files.
  • Most Recently Used List.

Before performing a registry scan, Registry Clean Pro scans all your hard drives to build a full list of the files and folders located there. This list is necessary to prevent incorrect deletion of the registry entries that refer to a file without specifying the full path.

For example, if a registry entry refers to a file as "notepad.exe" but not as "C:\Windows\ notepad.exe", Registry Clean Pro cannot determine the exact location of the file and verify its existence. In this case, Registry Clean Pro tries to locate this file in the list of files that was created during the scan of your hard drives. If one or more files with the name "notepad.exe" are found, Registry Clean Pro does not remove the corresponding entry from the registry.

Startup

HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

These two registry keys contain references to the executable files that are run automatically when your computer starts up.

If you move or delete such a file, the registry entry referring to this file becomes invalid since it no longer refers to an existing file. This might also happen when you uninstall an application incorrectly. In this case, the files belonging to the application are deleted, however the entries pointing to the deleted files still remain in the registry. This can cause delays and errors when you restart your computer.

Registry Clean Pro checks every entry in the Startup section, and if a file referenced by an entry cannot be found, Registry Clean Pro removes this entry from the registry.

If a registry reference to an executable file is specified as a short filename without the full path, Registry Clean Pro tries to find the file in all the folders on your hard drives. If the file in question is not found, the registry entry referring to this file is considered invalid and is removed from the registry. If one or more files with that name are found, Registry Clean Pro does not remove the reference from the registry. If a reference points to a file located on a network drive, Registry Clean Pro does not remove this reference.

Shared DLLs

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\SharedDLLs

This registry key contains references to shared DLLs (Dynamic Link Libraries). DLLs are used to store functions that can be called by programs to perform certain tasks. They can be shared by multiple applications to reduce memory and disk space requirements.

If a shared DLL is deleted or moved to another folder, the functions that are stored in this DLL become inaccessible to applications because the corresponding registry entry in the SharedDLLs section no longer points to the actual location of the DLL. This can cause problems for the applications that use functions stored in the missing DLL file.

If Registry Clean Pro cannot find a DLL file that is referenced from the SharedDLLs section, the registry entry pointing to this DLL is removed.

If a registry reference to a DLL file is specified as a short filename without the full path, Registry Clean Pro tries to find the file in all the folders on your hard drives. If the file in question is not found, the registry entry referring to this file is considered invalid and is removed from the registry. If one or more files with that name are found, Registry Clean Pro does not remove the reference from the registry. If a reference points to a file located on a network drive, Registry Clean Pro does not remove this reference.

Fonts

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Fonts (Windows 98/ME) or
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Fonts (Windows NT/2000/XP)

This section contains references to all the fonts installed on your computer. If you move or delete a font file referenced from this section using a program other than Windows Explorer, the registry entry pointing to this font becomes invalid as it refers to a font file that no longer exists.

If a reference to a missing font file remains in the Fonts registry section, the font may still appear in font lists but the font itself is inaccessible. This can cause problems for the applications that use this font or display font lists.

Registry Clean Pro scans every entry in the Fonts section to make sure that the corresponding font files are present. If a font file referenced from the Fonts section cannot be found, its entry is removed from the registry.

If a registry reference to a font file is specified as a short filename without the full path, Registry Clean Pro tries to find the file in all the folders on your hard drives. If the file in question is not found, the registry entry referring to this file is considered invalid and is removed from the registry. If one or more files with that name are found, Registry Clean Pro does not remove the reference from the registry. If a reference points to a file located on a network drive, Registry Clean Pro does not remove this reference.

Application Info

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\App Paths
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Uninstall

The first of these keys contains paths to the executable files of the applications installed on your computer. This is so Windows knows where the applications are located. The second key is used for storing the uninstall information.

If you delete an application directly from the Program Files folder instead of using the Uninstall function in the Windows Control Panel, references to the application path and uninstall information will still remain in the registry. This may cause problems when you try to uninstall the application from the Control Panel.

To ensure the validity of the "App Paths" section, Registry Clean Pro checks that all the application paths referenced from this section actually exist. If a path does not exist on the hard drive, the corresponding registry entry is deleted.

For the "Uninstall" section, Registry Clean Pro tries to locate all the uninstallers referenced from this section. If an uninstaller is missing, Registry Clean Pro removes the corresponding registry entry.

If a registry reference to an uninstaller is specified as a short filename without the full path, Registry Clean Pro tries to find the uninstaller file in all the folders on your hard drives. If the file in question is not found, the registry entry referring to this file is considered invalid and is removed from the registry. If one or more files with that name are found, Registry Clean Pro does not remove the reference from the registry. If a reference points to a file located on a network drive, Registry Clean Pro does not remove this reference.

COM/ActiveX

HKEY_CLASSES_ROOT\CLSID\<GUID>\InprocHandler
HKEY_CLASSES_ROOT\CLSID\<GUID>\InprocHandler32
HKEY_CLASSES_ROOT\CLSID\<GUID>\LocalServer32
HKEY_CLASSES_ROOT\CLSID\<GUID>\LocalServer
HKEY_CLASSES_ROOT\CLSID\<GUID>\PersistentHandler
HKEY_CLASSES_ROOT\CLSID\<GUID>\DefaultIcon
HKEY_CLASSES_ROOT\CLSID\<GUID>\InprocServer32
HKEY_CLASSES_ROOT\CLSID\<GUID>\InprocServer

The above keys contain references to COM and ActiveX objects. Before a COM/ActiveX object can be used by applications, a reference to this object must be created in the registry. If a registry reference describing a COM/ActiveX object points to a non-existing file, this reference is considered invalid.

Registry Clean Pro scans the above keys in the CLSID section to make sure that all the files referenced from this section actually exist. If a registry reference to a file is specified as a short filename without the full path, Registry Clean Pro tries to find the file in all the folders on your hard drives. If the file in question is not found, the registry entry referring to this file is considered invalid and is removed from the registry. If one or more files with that name are found, Registry Clean Pro does not remove the reference from the registry. If a reference points to a file located on a network drive, Registry Clean Pro does not remove this reference.

Note: The trial version of Registry Clean Pro does not scan the COM/ActiveX section of the registry. Purchase the full version of Registry Clean Pro to enable this function.

File Extensions

HKEY_CLASSES_ROOT
HKEY_CLASSES_ROOT\Applications
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts

These keys contain references to the registered file extensions. When you install a program, it automatically creates registry entries describing the file extensions associated with it. Later, when you double-click a file having one of these extensions, the program automatically opens it. For example, when you double-click a .txt file, it is automatically opened with Notepad because the .txt file extension is associated with Notepad.

If you uninstall a program incorrectly or an error occurs during the uninstall process, the file associations registered to this program may still remain in the registry, while the program itself is removed. This causes errors when you try to open a file with an extension associated with the removed program.

To check the validity of the registered file extensions, Registry Clean Pro scans the following registry sections:

1. File Extension Records. Registry Clean Pro makes sure that every file extension record in the HKEY_CLASSES_ROOT key is associated with a valid file type record. If a file extension record is linked to a non-existing type record, the entry is removed unless it has a valid Content Type value (this value allows Internet Explorer to correctly handle files downloaded from the Internet). If a file extension record contains a pointer to a GUID, this record is considered valid and is not removed. If a file extension key contains a ShellEx subkey, this key is considered valid and is not removed.

2. File Type Records. In the HKEY_CLASSES_ROOT section, Registry Clean Pro scans all the file type records that are referenced in the file extension records. For every file type record, Registry Clean Pro checks its default icon key and shell command keys. If the file specified in the default icon key cannot be found, this key is removed from the file type record. File type keys may contain nested shell command keys (for example, Open, Print or Print To). If a shell command key refers to a file that cannot be found on all the hard drives, Registry Clean Pro removes this key from the registry. The file type key itself is never deleted.

3. Application Keys for the Open With dialog. The HKEY_CLASSES_ROOT\Applications section contains references to the applications that appear in the Open With dialog box that is shown when you try to open a file that does not have an application associated with its extension. An application key may contain a default icon key and shell command keys. Registry Clean Pro checks all these nested keys to make sure they refer to existing files. If an application key refers to a file that cannot be found on all the hard drives, Registry Clean Pro removes this command from the application key. If a reference points to a file located on a network drive, Registry Clean Pro does not remove this reference. The application key itself is never deleted.

4. File Extensions for the Open With dialog. Registry Clean Pro checks all the file extensions in the HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts section. If a file extension record refers to a non-existing application key (see above), Registry Clean Pro removes this extension record from the registry. If you're still reading this, e-mail us the following line: HKEY_CURRENT_USER\Give\Me\AFreeCopyOf\RegistryCleanPro.

Note: The trial version of Registry Clean Pro does not scan the File Extensions section of the registry. You should purchase the full version of Registry Clean Pro to enable this function.

Shared Folders

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\lanmanserver\Shares (WinNT/2000/XP), or
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Network\LanMan (Windows 98/ME)

The above keys contain references to shared folders. You can make some of your folders accessible to other computers on your network. The settings for shared folders are stored in the registry to let Windows know which folders you want to share. If a shared folder is moved to another location or deleted incorrectly, its registry record becomes invalid since it no longer refers to a real folder.

Registry Clean Pro scans the Shared Folders section to make sure that all your shared folders are accessible. If a folder referenced from this section is missing or the specified path to this folder is invalid, Registry Clean Pro removes the corresponding entry from the Shared Folders section. The folder itself is never removed.

Help Files

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\Help
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\HTML Help

These registry keys store the paths to the help files registered by the applications installed on your computer. The corresponding registry entries are created when you install an application. The first key contains references to .hlp files and the second to .chm files. If you delete a help file or move it to another location, the registry entry referring to this help file becomes invalid because it no longer refers to an existing file.

If Registry Clean Pro cannot find a help file referenced from the Help Files section, the registry entry pointing to this file is removed.

If a registry reference to a help file is specified as a short filename without the full path, Registry Clean Pro tries to find the file in all the folders on your hard drives. If the file in question is not found, the registry entry referring to this file is considered invalid and is removed from the registry. If one or more files with that name are found, Registry Clean Pro does not remove the reference from the registry. If a reference points to a file located on a network drive, Registry Clean Pro does not remove this reference.

Most Recently Used List

HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\RunMRU

The registry stores the list of recently used files so you can quickly re-access them. If — due to an error — a reference to a file is invalid, there is no need for such a reference and it is safely removed from the registry.

Registry Clean Pro removes a reference to a recently used file if the corresponding file cannot be found or the specified path is invalid. If a reference points to a file located on a network drive, Registry Clean Pro does not remove the reference.

Note: Registry Clean Pro does not remove files from your hard drives.







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