0x03FFFFFF. The least significant bit (the right most bit) represents drive A, and the 26th bit from the right represents drive Z. A bit set to 1 disables AutoRun on a particular drive. For example, if the data value is set to 0x8 (1000 binary), AutoRun is disabled on drive D. Group Policy The only Group Policy settings available for AutoRun affect the Registry entries. The policy is available on either a per-machine or a per-user basis reflecting the Registry entry location in either HKLM or HKCU. As described above, a per-machine policy setting will cause the per-user policy setting to be ignored. When a policy is Enabled, Group Policy will add the entry to the Registry. If the policy is Disabled or set to Not configured, Group Policy deletes this entry from the Registry for the Machine policy (in HKLM) and sets it back to system defaults value for the User policy (in HKCU). System defaults may then take effect as described in the NoDriveTypeAutoRun section. The policy names, locations and possible settings vary slightly between Windows versions. The list of settings are relatively short and are always additional to the system default setting. Therefore, on Windows 2000, enabling the "Disable Autoplay" policy and setting it to "CD-ROM drives", disables AutoRun (as distinct from AutoPlay) for CD-ROM and DVD drives, removable drives, network drives, and drives of unknown type. This setting cannot be used to enable AutoRun on drives on which it is disabled by default or disable AutoRun for drives not listed. To disable or enable any particular drives or drive types, the Registry must be edited manually. Windows Server 2003, Windows XP, and Windows 2000 The per-machine policy location is: Group Policy \ Computer Configuration \ Administrative Templates \ System The per-user policy location is: Group Policy \ User Configuration \ Administrative Templates \ System The relevant policy is "Turn off Autoplay". In Windows 2000 the policy is called "Disable Autoplay" instead. Once the policy is Enabled it can be set to "All drives" or "CD-ROM drives". The latter setting adds CD-ROM drives to the existing list of disabled drive types as described above. Windows Vista, Windows Server 2008 The per-machine policy location is: Computer Configuration \ Administrative Templates \ Windows Components \ Autoplay Policies The per-user policy location is: User Configuration \ Administrative Templates \ Windows Components \ AutoPlay Policies The relevant policy is "Turn off