All About Registry

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default All About Registry

Post by JOHN2x on Sat Aug 16, 2008 3:54 am



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 it is
contained in two hidden files in your Windows directory, called
USER.DAT and SYSTEM.DAT, for Windows Me there is an additional
CLASSES.DAT file, while under Windows NT/2000 the files are contained
seperately in the %SystemRoot%\System32\Config directory. You can not
edit these files directly, you must use a tool commonly known as a
“Registry Editor” to make any changes (using registry editors will be
discussed later in the article).

<h3 class="smller">The Structure of the Registry</h3>

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.

[font_body]Each main branch (denoted by a folder icon in the Registry
Editor, see left) is called a Hive, and Hives contains Keys. Each key
can contain other keys (sometimes referred to as sub-keys), as well as
Values. The values contain the actual information stored in the
Registry. There are three types of values; String, Binary, and DWORD -
the use of these depends upon the context.

There are six main branches, each containing a specific portion of the information stored in the Registry. They are as follows:

• HKEY_CLASSES_ROOT - This branch contains all of your file association
mappings to support the drag-and-drop feature, OLE information, Windows
shortcuts, and core aspects of the Windows user interface.

• HKEY_CURRENT_USER - This branch links to the section of HKEY_USERS
appropriate for the user currently logged onto the PC and contains
information such as logon names, desktop settings, and Start menu

• HKEY_LOCAL_MACHINE - This branch contains computer specific
information about the type of hardware, software, and other preferences
on a given PC, this information is used for all users who log onto this

• HKEY_USERS - This branch contains individual preferences for each
user of the computer, each user is represented by a SID sub-key located
under the main branch.

• HKEY_CURRENT_CONFIG - This branch links to the section of
HKEY_LOCAL_MACHINE appropriate for the current hardware configuration.

• HKEY_DYN_DATA - This branch points to the part of HKEY_LOCAL_MACHINE,
for use with the Plug-&-Play features of Windows, this section is
dymanic and will change as devices are added and removed from the system

Each registry value is stored as one of five main data types:

• REG_BINARY - This type stores the value as raw binary data. Most
hardware component information is stored as binary data, and can be
displayed in an editor in hexadecimal format.

• REG_DWORD - This type represents the data by a four byte number and
is commonly used for boolean values, such as “0″ is disabled and “1″ is
enabled. Additionally many parameters for device driver and services
are this type, and can be displayed in REGEDT32 in binary, hexadecimal
and decimal format, or in REGEDIT in hexadecimal and decimal format.

• REG_EXPAND_SZ - This type is an expandable data string that is string
containing a variable to be replaced when called by an application. For
example, for the following value, the string “%SystemRoot%” will
replaced by the actual location of the directory containing the Windows
NT system files. (This type is only available using an advanced
registry editor such as REGEDT32)

• REG_MULTI_SZ - This type is a multiple string used to represent
values that contain lists or multiple values, each entry is separated
by a NULL character. (This type is only available using an advanced
registry editor such as REGEDT32)

• REG_SZ - This type is a standard string, used to represent human readable text values.

Other data types not available through the standard registry editors include:

• REG_DWORD_LITTLE_ENDIAN - A 32-bit number in little-endian format.

• REG_DWORD_BIG_ENDIAN - A 32-bit number in big-endian format.

• REG_LINK - A Unicode symbolic link. Used internally; applications should not use this type.

• REG_NONE - No defined value type.

• REG_QWORD - A 64-bit number.

• REG_QWORD_LITTLE_ENDIAN - A 64-bit number in little-endian format.

• REG_RESOURCE_LIST - A device-driver resource list.

<h3 class="smller">Editing the Registry</h3>

• 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 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

• Create a Shortcut to Regedit

This can be done by simply right-clicking on a blank area of your
desktop, selecting New, then Shortcut, then in the Command line box
enter “regedit.exe” and click Next, enter a friendly name (e.g.
‘Registry Editor’) then click Finish and now you can double click on
the new icon to launch the Registry Editor.

• Using Regedit to modify your Registry

Once you have started the Regedit you will notice that on the left side
there is a tree with folders, and on the right the contents (values) of
the currently selected folder.

• 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-click

<h3 class="smller">• Importing and Exporting Registry Settings</h3>

• 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:



• “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

It is also possible to delete keys and values using REG files. To
delete a key start by using the same format as the the REG file above,
but place a “-” symbol in front of the key name you want to delete. For
example to delete the [HKEY_LOCAL_MACHINE\SYSTEM\Setup] key the reg
file would look like this:



• 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:



• “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 has a number of command line options to help automate it’s use
in either batch files or from the command prompt. Listed below are some
of the options, please note the some of the functions are operating
system specific.

regedit.exe [options] [filename] [regpath]

[filename] Import .reg file into the registry

/s [filename] Silent import, i.e. hide confirmation box when importing files

/e [filename] [regpath] Export the registry to [filename] starting at [regpath]

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 [filename] Compress (Windows 98)

/D [regpath] Delete the specified key (Windows 98)

<h3 class="smller">Maintaining the Registry</h3>

How can you backup and restore the Registry?

Windows 95

Microsoft included a utility on the Windows 95 CD-ROM that lets you
create backups of the Registry on your computer. The Microsoft
Configuration Backup program, CFGBACK.EXE, can be found in the
\Other\Misc\Cfgback directory on the Windows 95 CD-ROM. This utility
lets you create up to nine different backup copies of the Registry,
which it stores, with the extension RBK, in your \Windows directory. If
your system is set up for multiple users, CFGBACK.EXE won’t back up the
USER.DAT file.

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.

Windows 98

Microsoft Windows 98 automatically creates a backup copy of the
registry every time Windows starts, in addition to this you can
manually create a backup using the Registry Checker utility by running
SCANREGW.EXE from Start | Run menu.

What to do if you get a Corrupted Registry

Windows 95, 98 and NT all have a simple registry backup mechanism that
is quite reliable, although you should never simply rely on it,
remember to always make a backup first!

Windows 95

In the Windows directory there are several hidden files, four of these
will be SYSTEM.DAT & USER.DAT, your current registry, and
SYSTEM.DA0 & USER.DA0, a backup of your registry. Windows 9x has a
nice reature in that every time it appears to start successfully it
will copy the registry over these backup files, so just in case
something goes wrong can can restore it to a known good state. To
restore the registry follow these instruction:

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:

cd c:\windows

<h3 class="smller">How can I clean out old data from the Registry?</h3>
Although it’s possible to manually go through the Registry and
delete unwanted entries, Microsoft provides a tool to automate the
process, the program is called RegClean. RegClean analyzes Windows
Registry keys stored in a common location in the Windows Registry. It
finds keys that contain erroneous values, it removes them from the
Windows Registry after having recording those entries in the Undo.Reg
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Post by +cdc.LEADTECH on Mon Aug 18, 2008 11:46 am

tnx for the infO mate :D :D


Hello Guest For now you Have 16777189 posts....ill hope you will post MORE and MORE!..

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Post by black_heart_pychzen029 on Thu Oct 02, 2008 8:37 am

thanks for sharing :D


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Post by jhegie on Sat Oct 04, 2008 7:17 am

its really hard to understand but tnx for the sharing... keep it up
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