the answer is: Last known good configuration
1) Last Known Good Configuration is saved each time a user logs on. or Registry settings collectively called the Last Known Good Configuration are saved in the registry each time the user successfully logs onto the system.
Using the regedit utility tool.Programmatically.Import a registry key.Use a different registry editor, eg a registry cleaner.Install a program.Warning:If you do not know much about computers or the registry settings, it is recommended that you do not change the settings as you could cause your computer to crash and/or be unable to start up. Even seemingly minor changes can lead to programs not working correctly.1. You can go to "run" & then write "regedit" there. The Registry Editor program will open to the root key. Using the interface, you can change your registry settings there.2. Use code to examine, insert, delete or change registry keys3. Have a registry file, and import it. Your computer may be set-up to automatically import keys upon clicking on such a file.4. There are many Registry Cleaner programs out there which can change registry settings. Warning, many are fake and are in fact malware/scareware designed to get you to buy programs or give out your information.5. Installing a program generally changes some registry settings automatically. This depends on the program.
Registry
They are located in the registry
A registry file, or most would called it "Windows Registry" is a database that stores hardware, software settings and options of Microsoft Windows Operating System.
System.dat was first used in Windows 95 and contains part of the Windows registry. The system registry is where all the Windows settings and most of the application and driver settings are stored. It is a very important file and should be left alone, though you could run a registry cleaner and a registry packer and reduce the size of it. Since XP and higher versions of Windows handle the registry more efficiently, it is best in the newer Windows versions to avoid most registry tools (though there is no harm in running a registry packer which does an internal defragmentation of the registry).
On a local PC you can have an access to registry settings through registry editor. It allows you to have a low-level access to system settings and export them to .reg file. Using registry editor you even can access to registry on a remote computer. But registry editor wasn't designed to work with multiple remote PCs simultaneously. If you need to export registry keys from multiple PCs, you can benefit from the features of EMCO Remote Registry Exporter. EMCO Remote Registry Exporter is a tool that was designed to work in the network environment to export registry keys from one or multiple remote PCs. It can be used it if you need to check registry data on remote PCs or backup specified registry keys. Registry keys and values are extracted by the application from remote PCs and are stored in .reg files, created for every PC, so you can use them to find required information or use later on to restore registry settings. To initiate remote registry export operation you only have to define a list of keys to export and a list of PCs where export should be performed
In a Windows-based computer, the system registry is a place designed for storing all of the settings within Windows and the applications. It is a collection of very important files that Windows needs to even boot. They store where everything is, all the settings, etc. Not all programs are compliant with the registry and may store their settings in private files. The registry was designed for getting away from all the settings file clutter and for having a common place for all settings for every application you use. Windows 3.1 used INI files, and while most versions of Windows will use them, the preferred place is the registry.
By default, a backup of the registry system is in My Documents. This can be changed in the system default settings.
This is a registry file kept in the registry and not in your documents. It contains personnel settings for each user. Leave this file alone.
You can not do that because virus uses programming to edit in registry. If you are trying to recover registry after virus has edited them then your efforts are worthless because best antivirus Kaspersky too fails to do that. This is because,registry is basically collection of settings which user wants for himself.Due to this reason any antivirus does not interfere with registry.
Registry cleaners are designed to keep your registry without any errors and also it will delete the unwanted entries in the registry so that your system will be more stable and fast. If you don't know how to do it. You also can use software to help you.