Troubleshooting and Configuring the Windows NT/95 Registry - D - A Closer Look at HKEY_CURRENT_CONFIG for Windows NT At startup, when multiple profiles are used in NT, the Last Known Good menu is automatically engaged, giving you the option of selecting which profile you would like to use. HKEY_CURRENT_CONFIG is the handle key representing the current hardware profile chosen at startup. Depending on the choice of profiles, one of the Registry hardware profile entries will be chosen. When that profile is loaded into the system, it will be loaded into both HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Hardware Profiles\Current and also into HKEY_CURRENT_CONFIG. Figure D.1 shows the results of the mapping. Figure D.1. HKEY_LOCAL_COMPUTER maps information directly to HKEY_CURRENT_CONFIG. After the system is started, any change to either location automatically updates the other. HKEY_CURRENT_CONFIG is used to make access to the configuration information easier for programmers. HKEY_CURRENT_CONFIG includes all of the details of the profile that is actually current in the system. The choice made during startup affects which of the two (or more) hardware profiles is current. For example, if Profile 0002 had been chosen, all of the Profile 0002 information would have been mapped into these keys. All of the settings in this appendix appear in the following format: Key Name Full path=Handle Key\Keyname Description, specific information, values Second-Level Key Name Full path=Handle Key\Keyname\Keyname Description, specific information, values Third-Level Key Name Full path=Handle Key\Keyname\Keyname\Keyname Description, specific information, values Additional Level Key Names Full path=Handle Key\Keyname\Keyname\Keyname\Keyname(\Keyname) Description, specific information, values Software HKEY_CURRENT_CONFIG\Software Without any software difference between the available profiles, there is nothing listed here. If the selected profile included software specific to hardware that was only present during this profile, it would be listed here. That is extremely rare. In nearly all cases, the Software entry is here for future expansion possibilities, particularly when full Plug and Play is implemented in Windows NT. System HKEY_CURRENT_CONFIG\System This key holds all the subkeys for settings that are unique to the currently installed profile. CurrentControlSet HKEY_CURRENT_CONFIG\System\CurrentControlSet This key holds subkeys for Control, Enum, and Services. Control HKEY_CURRENT_CONFIG\System\CurrentControlSet\Control Availability of the Control Panel functions might be different depending on the hardware activated. If there is a difference, it is listed here. Class HKEY_CURRENT_CONFIG\System\CurrentControlSet\Control\Class Different icons for the Control Panel are listed here if necessary. Enum HKEY_CURRENT_CONFIG\System\CurrentControlSet\Enum This key holds information about additional buses that might be available in a hardware profile. For example, a docking station that includes a separate bus would be listed and configured here. Services HKEY_CURRENT_CONFIG\System\CurrentControlSet\Services Any differences in loaded drivers based on the hardware profile are listed as subkeys to this key. s3 HKEY_CURRENT_CONFIG\System\CurrentControlSet\Services\s3 This video driver is different because it can run a higher default resolution with a different monitor. Those settings are in the following key: HKEY_CURRENT_CONFIG\System\CurrentControlSet\Services\s3\Device0 Summary HKEY_CURRENT_CONFIG allows software and device-driver programmers to easily update the Registry, without concern for multiple profile information. The same data is in HKEY_LOCAL_MACHINE, and any Registry change will update both locations simultaneously.

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