Introduction to the Registry

The registry is a system-defined database in which applications and system components store and retrieve configuration data, information and settings for all the hardware, operating system software, most non-operating system software, users, preferences of the personal computer, etc. The data stored in the registry varies according to the version of Windows used.

Note: in the latest Windows versions - Windows XP, Windows Vista and Windows 7 - the registry does not physically exist as a single file, it is a virtual entity composed of different files in the system, some of which are created during the system boot and exist only during the Windows user session and are deleted once the computer is shut down.

If there is an error in the registry, your system may not function properly. AVS Registry Cleaner helps you scan your registry for some possible problems and try and fix them to improve the overall computer performance.

Note: most of the registry changes in Windows versions require a user to have Administrator permissions to perform them; in Windows Vista and Windows 7 you will additionally need to run the program as administrator to get the full access to all the program features.

Note: it is not recommended to edit the registry data unless it is absolutely necessary, that is your computer experiences slow performance issues, some programs behave inadequately and so on. Please make sure you create a backup each time you scan and fix some registry problems.

The registry contains the following root hives:

• HKEY_CLASSES_ROOT (HKCR) - stores information about the system registered applications, such as file extensions tying them to the applications used to handle these extensions. In fact this hive combines data from the HKLM\Software\Classes and HKEY_USERS\Current_User's_SID_Classes registry sections.

• HKEY_CURRENT_USER (HKCU) - stores settings that are specific to the currently logged-in user.

• HKEY_LOCAL_MACHINE (HKLM) - stores settings that are general to all users on the computer - information about system hardware drivers, services, software and Windows settings.

• HKEY_USERS (HKU) - contains subkeys corresponding to the HKEY_CURRENT_USER keys for each user profile actively loaded on the machine, though user hives are usually only loaded for currently logged-in users.

• HKEY_CURRENT_CONFIG - contains information gathered at runtime; information stored in this key is not permanently stored on disk, but rather regenerated at the boot time.

Below is the list of registry sections, which are scanned by AVS Registry Cleaner:

• COM/ActiveX - registry section in which the COM-servers used by various applications are registered (in-process servers (.dll files) or out-of-process servers (.exe files)). The program scans for the .dll or .exe links in the registry that point to the nonexistent files on the computer hard disk drive. A COM-server can also link to a type library (usually a .tlb-file) that does not exist. In case the DefaultIcon registry subkey is present in the category, the program will also scan for the presence or absence of the file containing the file icons. The registry hives scanned by AVS Registry Cleaner are:

  • HKLM\Software\Classes
  • HKU_Classes

• Application Paths - registry section used to store the full paths to the applications launched using the Run window or command prompt. The program scans for the nonexistent paths to the applications and deletes the entries if these files could not be found. The registry hive scanned by AVS Registry Cleaner is:

  • HKLM\Software\Microsoft\Windows\CurrentVersion\App Paths\

• Uninstall Entries - registry section used for programs installation/deinstallation paths entries. The program scans for the nonexistent paths to the applications installer/uninstaller files and deletes the entries if these files could not be found. The registry hives scanned by AVS Registry Cleaner are:

  • HKLM\Software\Microsoft\Windows\CurrentVersion\Uninstall\
  • HKU\Software\Microsoft\Windows\CurrentVersion\Uninstall\

• File Extensions - registry section used to store the full paths to the applications, file icons and additional commands associated with the file extensions. The program scans for the nonexistent paths to the applications and deletes the entries if these files could not be found. The registry hives scanned by AVS Registry Cleaner are:

  • HKLM\Software\Classes
  • HKU_Classes

• Windows Fonts - registry section used to store the full paths to the Windows fonts or the font file name (in this case the font file must be present in the \Windows\Fonts\ directory). The program scans for the nonexistent paths to the font files and deletes the entries if these files could not be found. The registry hive scanned by AVS Registry Cleaner is:

  • HKLM\Software\Microsoft\Windows NT\CurrentVersion\Fonts

• Help Files - registry section used to store the full paths to the Windows programs helps. The program scans for the nonexistent paths to the helps files and deletes the entries if these files could not be found. The registry hives scanned by AVS Registry Cleaner are:

  • HKLM\Software\Microsoft\Windows\Help
  • HKLM\Software\Microsoft\Windows\HTML Help

• Internet Explorer typed URLs - registry section used to store the history of the URL-addresses typed in the Internet Explorer address bar. The program scans for the presence of these entries. The registry hive scanned by AVS Registry Cleaner is:

  • HKU\Software\Microsoft\Internet Explorer\TypedURLs

• Explorer MRU^* list - registry section used to store the history of the entered Run window commands, recent documents list, last visited pages and opened and saved files. The program scans for the presence of these entries. The registry hives scanned by AVS Registry Cleaner are:

  • HKU\Software\Microsoft\Windows\CurrentVersion\Explorer\RunMRU
  • HKU\Software\Microsoft\Windows\CurrentVersion\Explorer\RecentDocs
  • HKU\Software\Microsoft\Windows\CurrentVersion\Explorer\ComDlg32\LastVisitedMRU
  • HKU\Software\Microsoft\Windows\CurrentVersion\Explorer\ComDlg32\OpenSaveMRU

• Search Assistant MRU^* list - registry section used to store the history of the entered Search window commands. The program scans for the presence of these entries. The registry hives scanned by AVS Registry Cleaner are:

  • HKU\Software\Microsoft\Search Assistant\ACMru\5001
  • HKU\Software\Microsoft\Search Assistant\ACMru\5603
  • HKU\Software\Microsoft\Search Assistant\ACMru\5004
  • HKU\Software\Microsoft\Search Assistant\ACMru\5647

• Media MRU^* list - registry section used to store the history of the latest media files played by the Windows Media Player. The program scans for the presence of these entries. The registry hives scanned by AVS Registry Cleaner are:

  • HKU\Software\Microsoft\MediaPlayer\Radio\MRUList
  • HKU\Software\Microsoft\MediaPlayer\Player\RecentURLList
  • HKU\Software\Microsoft\MediaPlayer\Player\RecentFileList

• Shared DLLs - registry section used to store the full paths to the library files (DLLs) that can be used by several programs. The program scans for the nonexistent paths to the files and deletes the entries if these files could not be found. The registry hive scanned by AVS Registry Cleaner is:

  • HKLM\Software\Microsoft\Windows\CurrentVersion\SharedDlls

• Sounds and App Events - registry section used to store the full paths to the Windows sound files used by various applications. The program scans for the nonexistent paths to the sound files and deletes the entries if these files could not be found. The registry hive scanned by AVS Registry Cleaner is:

  • HKU\AppEvents\Schemes\Apps\

• Windows Startup - registry section used to store the full paths to the applications which are executed automatically during the system startup. The program scans for the nonexistent paths to the files and deletes the entries if these files could not be found. The registry hives scanned by AVS Registry Cleaner are:

  • HKLM\Software\Microsoft\Windows\CurrentVersion\Run
  • HKU\Software\Microsoft\Windows\CurrentVersion\Run

Note: AVS Registry Cleaner searches not only the HKEY_CURRENT_USER registry hive, but also the HKEY_USERS that store data for all the users on the computer. Please make sure you do backup your windows registry before you fix the existing problems.