Repair Windows Registry

Windows Registry in Earlier Versions of Windows

Registry Key and Registry Value

• HKEY_CLASSES_ROOT: This key has sub keys that store data of registered applications, file associations, and OLE object class IDs. These data ensure that when a program is executed then the right program is executed.  
• HKEY_CURRENT_USER: This key stores information and settings of the current user. These settings include the screen color, background image, and many other personal settings.
• HKEY_LOCAL_MACHINE: This key contains configuration data about the computer. The registry files that store this information are SAM, SYSTEM, SECURITY, and SOFTWARE.
• HKEY_USERS: This key contains data about all the users that are created on that system.
• HKEY_CURRENT_CONFIG: This key contains hardware configuration of the local computer that is used by the operating system while booting. The files that store this information are SYSTEM and NTUSER.dat.
• HKEY_DYN_DATA: This key is only available in Windows 95/98/ME. This contains information about hardware, plug play devices, and their configuration. The data is not persistent but is created after booting and destroyed on turned off.

• REG_NONE: No type
• REG_SZ: A string value type
• REG_EXPAND_SZ: An expandable string value that can contain environment variables
• REG_BINARY: Binary data
• REG_DWORD / REG_DWORD_LITTLE_ENDIAN: An integer between 0 and 4,294,967,295
• REG_DWORD_BIG_ENDIAN: An integer between 0 and 4,294,967,295.
• REG_LINK: symbolic link
• REG_MULTI_SZ: An array of unique strings
• REG_RESOURCE_LIST: Resource list
• REG_FULL_RESOURCE_DESCRIPTOR: Resource descriptor
• REG_RESOURCE_REQUIREMENTS_LIST: Resource requirements list
• REG_QWORD / REG_QWORD_LITTLE_ENDIAN: A 64-bit integer that was introduced in Windows 2000

Cause of Registry Key Corruption

• Improper Shutdown/Power Fluctuation: When the computer is in running state, it keeps record of all the changes made in registry. These changes are finally written in the system registry file when the system is being turned off. When the computer is turned off improperly due to power fluctuation/failure, or intentionally by the user, the final registry changes are not saved. This leads to wrong entries in the registry.  Corrupt registry files can stop the operating system from working properly.
• Improper Uninstall: During uninstall process, it may be possible that some of the registry information is not deleted, or it may be possible that some information is left in some other user account. The ‘Orphan Keys’ left behind in the windows registry can slow other programs while starting. And also, the place occupied by the registry key is left void after uninstalling the hardware/software making the system slower.
• Improper Re-install: When software is installed again after removing it. Then duplicate or multiple entries of the software can be written in the registry file. This can cause inconsistency in the entries causing the software to run slowly or not run at all.
• Virus/Malware/Spyware: People with malicious intention can try to damage your system be sending Virus, Trojan or any other spying programs. These programs can steal the registry entries, duplicate them, add new undeletable entries, corrupt them, or even delete them. 

Recommended Software to Repair Windows Registry Errors

Stellar Phoenix Registry Manager to Repair Windows Registry Errors

Manual Methods to Repair Windows Registry Errors

• Editing: Windows provides ‘regedit.exe’ application to read and edit the registry. Many also provide Regedit32.exe, but it is know just a stub to evoke Regedit.exe. The editor can read, create, edit, and delete the entries in the registry. It can also be used to grant registry permissions to other users by the administrator.
  To edit the registry, click on the ‘Run’ option in the ‘Start’ menu. Write ‘regedit’ and click OK. This will start the editor. Right-click on the names under the Name column, and choose to rename, modify, or delete the key-value. Right click on the left pane to create new keys in the opened key hierarchy.
• Store Backup: Registry editor provides options to store backup of whole registry or partially of some keys. In the registry editor, click on ‘File’ menu in the registry editor and click on ‘Save’ to store in form of .REG files. These file are text files saved in the hard disk that can be imported by the system at any point of time. You can also make changes in the file to create new key, delete key, and key value to create a new registry. Data is stored in the REG file as:
• Hive NameKey NameSub key Name
• Value Name=Value type: Value data
• Add (-) sign before key name (- HKEY_CURRENT_USER\Software) to delete that key. You can add new values to keys by writing new values down the older values. Delete values by writing a (-) sign after = in the value name.
• Backup facility of windows: This is a backup utility that backup registry files along with other important system files. To open this, Click ‘Start’ and move to ‘All Programs→ Accessories → System Tools → Back Up’. Click on the ‘Advance Mode’ link in the starting screen. Click ‘Backup’ tab in the Backup application. Choose ‘System State’ in the directory and click ‘Start Backup’ button. A copy of registry files will be saved. Directly click on this saved file to restore when needed. To backup the system state through DOS prompt write the command, ‘ntbackup backup systemstate bks file’ name on the prompt. The file is to be created in the GUI version of ntbackup.exe utility. There are various parameters available for this command. Window registry will be saved along with the system state backup which can be used to restore at a later stage.
• Restore Backup: Click on the File menu in the registry editor and click on the ‘Import’ option to import saved registry. To import a backed up registry file through DOS prompt type regedit.exe /s file name on the prompt.
• Other Options: There are many more application APIs like, RegCloseKey, RegCreateKey, RegSaveKey, RegLoadKey, etc., that can help in editing registry files. Other than these methods, ‘Boot from Last Known Good Configuration’ option is also helpful in restoring to a good registry state during problematic times. There is also a ‘policy’ option in the registry files that restricts users, who do not have administrative privilege, to make changes in the window registry.