File Extensions - REG File Format

SUMMARY: Provides details of the .REG file format in Windows used by the Registry Editor.

The Windows Registry is the main repository of configuration information for Windows and most applications. For Windows users, the .REG file extension represents text files that can be imported to change settings in this repository. In some cases this bypasses the Control Panel and other means of configuring program and application settings, and in other cases this provides ways of changing information that cannot be changed (or changed easily) through graphical interfaces.

Beneficial .REG files and registry changes can solve problems such as applications not letting you customize their toolbars, Windows not letting you change the desktop wallpaper, or removing an extraneous link to your computer manufacturer's website from the "Start" menu.

However, note that specially-crafted .REG files can conceivably crash your computer and make Windows unbootable, among other problems. You should only double-click .REG files received from a trustworthy source, known to perform a specific task that you need done on your machine, and even then, still be careful!

Before double-clicking a .REG file, make sure it is actually a .REG file and not some application masquerading as Registry information. You can determine this by turning on file extension viewing in Explorer, helping make sure that a file "update_settings.reg", for example, is not actually "update_settings.reg.exe", an application claiming to be a plain-text registry file.

To turn this feature on, first open any folder in Explorer.

If you are using Windows 95 / 98 / ME / NT 4.0 / 2000 / XP:

1. Select "Tools" - "Folder Options".
2. When the "Folder Options" dialog box appears, click the "View" tab.

If you are using Windows Vista:

1. Open any folder in Explorer.
2. Click the "Organize" button, selecting "Folder and Search Options".

Now:

3. Uncheck "Hide extensions for known file types".
4. Click "OK".

For those wanting more information, a couple of example .REG files are listed below, between the "---" dividers. The first one enables the "Tools" - "Internet Options" feature of Internet Explorer 7 if such feature has been accidentally disabled, disabled via an anti-malware application, or disabled by malware itself:

---
Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Policies\Microsoft\Internet Explorer\Restrictions]
"NoBrowserOptions"=dword:00000000

---

And this .REG file re-enables Windows XP's "Settings" page in the Display Properties dialog box if somehow it has become invisible:

---

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system]
"nodispsettingspage"=dword:00000000

---

(Note that these are provided for example purposes only - you should NOT try using them without copying and pasting the information CAREFULLY into .REG files, and only use these if you absolutely know what you're doing!)

While explaining exactly how these .REG files work, as well as each section of the Windows Registry, is outside the scope of this article, understand that Windows recognizes these plain-text .REG files as information that can be imported into Windows to configure a variety of system and software settings.

Besides double-clicking premade .REG files, the Windows Registry can be modified directly by using the Registry Editor application. While the Windows Registry should be ok to browse, modifying information without knowing what you are doing can have disastrous consequences, including and not limited to keeping your computer from booting.

To access this application:

If you are using Windows 95 / 98 / ME / NT 4.0 / 2000 / XP:

1. Click on the "Start" button.
2. Click "Run".
3. Type "regedit" (without quotes) and press ENTER.

If you are using Windows Vista:

1. Click on the "Start" button.

2. Type "regedit" (without quotes) and click on the "regedit.exe" link when it appears.

3. If you have UAC (User Account Control) enabled, confirm you wish to open the Registry Editor.

In summary, .REG files, representing Windows Registry changes, allow one to quickly and easily make modifications to system and application settings that would normally require opening the (foreboding) Registry Editor. Before double-clicking such files to modify your system, first make sure they are legitimate. Malicious registry files can harm your system, and masquerading files can conceivably install all types of malware. Legitimate .REG files, however, can help you make changes to your computer that might otherwise require the help of those with extensively more knowledge of system settings.

Note that this article discusses very technical information and the author disclaims any responsibility for the use of information provided. Read the disclaimer.