How to Test Autorun.inf Files (136214)

SUMMARY

AutoPlay is enabled by the new 32-bit, protected-mode driver architecture in Microsoft Windows 95 and Microsoft Windows 98. Because the operating system can now detect the insertion of media in a CD-ROM drive, it has the opportunity to do some intelligent processing whenever this occurs.

By default, Windows 95 and Windows 98 only check for an Autorun.inf file when a CD-ROM disc is inserted into the CD-ROM drive. However, you may want to test for syntax and logic errors before burning a CD-ROM disc. This article explains how.

MORE INFORMATION

In Windows 9x, whenever a CD-ROM disc is inserted, the shell immediately checks to see if the CD-ROM disc has a PC filesystem. If it does, Windows 9x looks for a file named Autorun.inf. If the file exists, Windows 9x follows the instructions contained in the file, which usually involves running a setup application of some sort.

However, by changing a setting in the Windows 9x registry, you can have the Shell use AutoPlay on any media, including shared network drives and floppy disks.

The registry key that needs to be modified is:

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

This key, which is of type REG_BINARY, consists of four bytes. The first byte is a bitmask defining which drive types should be AutoRun. The other three bytes should be set to zero (0).

The bits in the bitmask correspond to these constants:

Type                Bit
DRIVE_UNKNOWN       0
DRIVE_NO_ROOT_DIR   1
DRIVE_REMOVABLE     2
DRIVE_FIXED         3
DRIVE_REMOTE        4
DRIVE_CDROM         5
DRIVE_RAMDISK       6

Setting a bit in the bitmask prevents you from using AutoPlay with the corresponding drive type. By default, the value in the registry is 0x95. Bits 0, 2, 4 and 7 are therefore set, which means that drive types DRIVE_UNKNOWN, DRIVE_REMOVEABLE, and DRIVE_REMOTE don't use AutoPlay information. (Bit 7 is set to cover future device types.) Altering this registry value thus allows you to test Autorun.inf files from a floppy disk (DRIVE_REMOVEABLE), network drive (DRIVE_REMOTE), and so on. For example, to be able to test AutoPlay from a floppy disk, set the value of the first byte to 0x91 to enable AutoPlay for floppy disks.

NOTE: Most floppy disk drive controllers do not currently recognize when a floppy disk has been inserted. To test AutoPlay on a floppy disk, first alter the registry setting so that bit DRIVE_REMOVEABLE is not set, start the Windows Explorer, insert the floppy disk, and press the F5 key to refresh the display.

To test the Autorun.inf file on a given disk, using the right mouse button, click the icon for the drive in the Windows Explorer. The effects of the Autorun.inf file should be visible in the context menu.