What Is The Registry?
What is the Registry?
The Registry is a database used to store settings and options for the 32 bit versions of Microsoft Windows including Windows 95, 98, ME and NT/2000. It contains information and settings for all the hardware, software, users, and preferences of the PC. Whenever a user makes changes to a Control Panel settings, or File Associations, System Policies, or installed software, the changes are reflected and stored in the Registry.
The physical files that make up the registry are stored differently depending on your version of Windows; under Windows 95, 98 & ME it is contained in two hidden files in your Windows directory, called USER.DAT and SYSTEM.DAT, while under Windows NT/2000 the files are contained separately in the %SystemRoot%\System32\Config directory. You can not edit these files directly, you must use a tool usually known as a "Registry Editor" to make any changes (using registry editors will be discussed later in the article).
The Structure of the Registry
The Registry has a hierarchal structure, although it looks complicated the structure is similar to the directory structure on your hard disk, with Regedit being similar to Windows Explorer.
There are six main branches, each containing a specific portion of the information stored in the Registry. They are as follows:
Each registry value is stored as one of five different data types:
Editing the Registry
The Registry Editor (REGEDIT.EXE) is included with most version of Windows (although you won't find it on the Start Menu) it enables you to view, search and edit the data within of the Registry. There are several methods for starting the Registry Editor, the simplest is to click on the Start button, then select Run, and in the Open box type "regedit", and if the Registry Editor is installed it should now open and look like the image below.
An alternative Registry Editor (REGEDT32.EXE) is available for use with Windows NT/2000, it includes some additional features not found in the standard version, including; the ability to view and modify security permissions, and being able to create and modify the extended string values REG_EXPAND_SZ & REG_MULTI_SZ.
Create a Shortcut to Regedit
Using Regedit to modify your Registry
Like Windows explorer, to expand a certain branch (see the structure of the registry section), click on the plus sign [+] to the left of any folder, or just double-click on the folder. To display the contents of a key (folder), just click the desired key, and look at the values listed on the right side. You can add a new key or value by selecting New from the Edit menu, or by right-clicking your mouse. And you can rename any value and almost any key with the same method used to rename files; right-click on an object and click rename, or click on it twice (slowly), or just press F2 on the keyboard. Lastly, you can delete a key or value by clicking on it, and pressing Delete on the keyboard, or by right-clicking on it, and choosing Delete.
Note: it is always a good idea to backup your registry before making any changes to it. It can be intimidating to a new user, and there is always the possibility of changing or deleting a critical setting causing you to have to reinstall the whole operating system. It's much better to be safe than sorry!
Importing and Exporting Registry Settings
A great feature of the Registry Editor is it's ability to import and export registry settings to a text file, this text file, identified by the .REG extension, can then be saved or shared with other people to easily modify local registry settings. You can see the layout of these text files by simply exporting a key to a file and opening it in Notepad, to do this using the Registry Editor select a key, then from the "Registry" menu choose "Export Registry File...", choose a filename and save. If you open this file in notepad you will see a file similar to the example below:
REGEDIT4 [HKEY_LOCAL_MACHINE\SYSTEM\Setup] "SetupType"=dword:00000000 "CmdLine"="setup -newsetup" "SystemPrefix"=hex:c5,0b,00,00,00,40,36,02
The layout is quite simple, REGEDIT4 indicated the file type and version, [HKEY_LOCAL_MACHINE\SYSTEM\Setup] indicated the key the values are from, "SetupType"=dword:00000000 are the values themselves the portion after the "=" will vary depending on the type of value they are; DWORD, String or Binary.
So by simply editing this file to make the changes you want, it can then be easily distributed and all that need to be done is to double-click, or choose "Import" from the Registry menu, for the settings to be added to the system Registry.
Deleting keys or values using a REG file
The format used to delete individual values is similar, but instead of a minus sign in front of the whole key, place it after the equal sign of the value. For example, to delete the value "SetupType" the file would look like:
REGEDIT4 [HKEY_LOCAL_MACHINE\SYSTEM\Setup] "SetupType"=-
Use this feature with care, as deleting the wrong key or value could cause major problems within the registry, so remember to always make a backup first.
Regedit Command Line Options
regedit.exe [options] [filename] filename Import .reg file into the registry /s Silent, i.e. hide confirmation box when importing files /e Export registry file e.g. regedit /e file.reg HKEY_USERS\.DEFAULT /L:system Specify the location of the system.dat to use /R:user Specify the location of the user.dat to use /C Compress [filename] (Windows 98)
Maintaining the Registry
How can you backup and restore the Registry?
After you have backed up your Registry, you can copy the RBK file onto a floppy disk for safekeeping. However, to restore from a backup, the RBK file must reside in the \Windows directory. Windows 95 stores the backups in compressed form, which you can then restore only by using the CFGBACK.EXE utility.
What to do if you get a Corrupted Registry
1. Click the Start button, and then click Shut Down.
2. Click Restart The Computer In MS-DOS Mode, then click Yes.
3. Change to your Windows directory. For example, if your Windows directory is c:\windows, you would type the following:
4. Type the following commands, pressing ENTER after each one. (Note that SYSTEM.DA0 and USER.DA0 contain the number zero.)
attrib -h -r -s system.dat attrib -h -r -s system.da0 copy system.da0 system.dat attrib -h -r -s user.dat attrib -h -r -s user.da0 copy user.da0 user.dat
5. Restart your computer.
Following this procedure will restore your registry to its state when you last successfully started your computer.
If all else fails, there is a file on your hard disk named SYSTEM.1ST that was created when Windows 95 was first successfully installed. If necessary you could also change the file attributes of this file from read-only and hidden to archive to copy the file to C:\WINDOWS\SYSTEM.DAT.
How can I clean out old data from the Registry?
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