Prior to Windows 95, all configuration information related to your operating system, programs installed on it and hardware devices connected to it was saved in separate INI files. At that time computers had very small and expensive storage space and system memory. And, having several INI files on the disk not only cluttered the hard disk and consumed loads of storage space, but also ate up a lot of system memory.
To counter these problems, Microsoft did away with INI files and took a giant leap by introducing the Windows registry with the Microsoft Windows 95 operating system. The registry has since stayed with all Windows operating systems including the latest Microsoft Windows Vista operating system, and is basically a centralized, hierarchal, tree-like database repository, in which all configuration information related to the software and hardware installed on your PC is stored. The registry also contains user preferences and system setup information.
To view the registry tree on your Windows computer, open Start menu, select Run, type regedit and then click on the OK button. This will open the Registry Editor window. In this window, you will see two panes. In the left pane, you will see the five main keys, also referred to as root keysHKEY_CLASSES_ROOT, HKEY_CURRENT_USER, HKEY_LOCAL_MACHINE, HKEY_USERS, and HKEY_CURRENT_CONFIG. Out of these HKEY_USERS and HKEY_LOCAL_MACHINE are the real root keys and the other three are mirrors of these two keys. When you expand these root keys, you will see that each of them comprise several subkeys and sub-subkeys. Each key comprises zero or more values, which are displayed in the right pane.
Let us now have a look at the type information contained within each root key of the registry.
- The branch of the HKEY_USERS or HKU key includes data for all user profiles on your computer. This key also comprises template information that is used when you create a new user profile on the PC.
- The HKEY_CURRENT_USER or HKCU is a mirror of the HKU key. This key contains the root of the configuration for the user account with which you have currently logged on to your system. User-related information such as folder, screen appearance, and Control Panel settings are saved in this folder and this user-specific information is referred as user profile.
- The branch of the HKEY_LOCAL_MACHINE or HKLM key consists of hardware and software configuration information of your computer for all users configured on the system.
- The HKEY_CLASSES_ROOT or HKCR is a mirror of the HKEY_LOCAL_MACHINE\Software key. The information contained in this key ensures that when you open a file on your system, it is opened using the correct program.
- The HKEY_CURRENT_CONFIG or HKCC is also a mirror of the HKLM key and it comprises data about the hardware profile used by the local computer during system startup.
When you start working on the computer various programs and hardware devices on the system refer to the registry for information that enables them to function correctly on the system. In the process, a large amount of data is added to and removed from the registry in just a few minutes.
This high to and fro traffic within the registry makes it quite vulnerable to the accumulation of obsolete and invalid data that unnecessarily causes the registry to grow to a very large size. A large registry slows down and takes longer time to answer the queries sent to it by programs and hardware on your computer and thus results in the slowing down of your system. Moreover, a large registry easily gets corrupted and starts generating frequent errors on your system. In more severe cases, a damaged registry may render your system unbootable.
To prevent your PC suffering from registry-related problems, it is recommended that you regularly perform registry cleanup and repair to keep it free from unwanted and erroneous information. You can do this easily with the help of a reliable and efficient Windows registry cleaner tool. Registry tools are easy to use and provide you with several benefits. You can use these tools to perform automatic scan and repair of the registry, perform registry defrag to consolidate and compress its files to enhance data access time, and to easily make regular registry backups that you can use to restore the Windows registry in case an irreversible error occurs that causes the current registry to fail.