What is inside Autorun.inf?

Autorun.inf is a text file and in its basic form it look like this:

[AutoRun]
OPEN=MYAPP.EXE

The OPEN command specifies which program that should be run when the CD/DVD is inserted in the drive. In the example above a program with the name MYAPP.EXE will be executed.

Autorun.inf can also specify an icon that will represent your application's CD or DVD in the Windows user interface (for example in Windows Explorer). To specify a new icon to the CD/DVD drive, Autorun.inf should contain the following commands:

[AutoRun]
OPEN=MYAPP.EXE
ICON=MYICON.ICO

The ICON command specifies the filename of the new icon to display. In this case an icon with the filename MYICON.ICO will be used.

In the examples above the program file and the icon file most be located in the root directory of the CD/DVD, but you can also access files located in a sub directory on the CD/DVD if you specify a relative path. Example:

[AutoRun]
OPEN=FOLDER\MYAPP.EXE

The OPEN and ICON commands are the most used in Autorun.inf files, but there are more commands available. You can for example specify a new disc label with the LABEL command. The LABEL command has the benefit that you can specify labels that contains more than 16 characters (16 is the normal limit for CD/DVD labels).

A list and a description of the commands that can be used in Autorun.inf can be found at the following page: Autorun.inf - Commands. If you want a more detailed information about the commands you can also take a look at the following Microsoft page: Autorun.inf Entries.

Is it possible to show documents automatically with Autorun.inf?

In newer windows it is possible, but in older Windows it is not. There is a command named SHELLEXECUTE that can open documents if the filename extension (.doc, .avi, .pdf etc) is registered in the system. But if you distribute a commercial application that should work in all Windows versions it is recommended not to use this command because this command will not work in for example Windows 95 or 98. Use instead a document launcher application that works in all Windows versions. A document launcher application will take a path to the document file as a parameter and open the dokument by calling proper functions in the system. An example of a document launcher application is SamLogic Autorun Creator.

In Windows XP there is also a new technology, called AutoPlay, that automatically opens documents on CD's and DVD's. AutoPlay will detect content such as pictures, music, or video files and then automatically launch an application to play or show the content. This technology is not available in older Windows.

In some computers the AutoRun feature do not seems to work, why?

As mentioned before, all Windows since Windows 95 have the AutoRun technology built-in, but in some computers this feature can be disabled. Administrators can disable this features in client computers on a network for security reasons and some applications, for example CD burning programs, can sometimes also disable this feature. 

If AutoRun is disabled on a computer you can enable it by changing a value in the registry. There is a value with the name NoDriveTypeAutoRun at the following key:  

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer

that probably is B5 (hexadecimal). If that is the case, you can change it to the hexadecimal value 95 and then restart the computer. After the reboot the computer should have the AutoRun feature enabled again.

The NoDriveTypeAutoRun value contains a bit mask where every bit that is set disables a drive type. The default value for NoDriveTypeAutoRun is 95, giving the bit pattern 10010101. Bit number 5 enables/disables AutoRun on CD-ROM drives and as default this bit is cleared (zero). By setting this value to B5, the bit number 5 will be set (one) and the CD-ROM drive is disabled. The bit pattern for B5 is 10110101.

It's also possible to enable/disable AutoRun on other drive types than CD-ROM by clearing/setting other bits in the NoDriveTypeAutoRun value. For example it's possible to have AutoRun enabled for floppy disks. In the table below you find some of the bits and what drive types they represent.

Bit 2 = Disk can be removed from drive (such as a floppy disk)
Bit 3 = Disk cannot be removed from drive (a hard disk)
Bit 4 = Network drive
Bit 5 = CD-ROM drive
Bit 6 = RAM disk

To enable AutoRun you must clear the corresponding bit. You can read more details about enabling/disabling the AutoRun feature at the Microsoft page: Enabling and Disabling AutoRun.


This article refers to:
SamLogic CD-Menu Creator 2008

Other articles
More articles are available from the article index page.