Changing Driver Loading Controls in the Registry

Under most circumstances, you should define the startup behavior of a device or a service by choosing the Devices icon or the Services icon in Control Panel, or by using Server Manager in Windows NT Server. Use these procedures in specific cases where you cannot define behavior using the other administrative tools.

You can change the basic value entries in the Registry for a specific driver to control driver loading. For example, you can change these things:

When the driver is loaded or the service is started, including turning off driver loading during startup
The load order for a driver, a service, or a group during system startup
Error control for a driver or service, so that startup continues or halts, depending on whether the item is initialized
Parameters that can be set for a driver or service

To change the behavior of a driver or service

Select the subkey for the driver or service in the following Registry path:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet
\Services\DriverName
If you want to change how system startup proceeds if the driver is not loaded or the service is not started, change the value of ErrorControl as follows:

Error control	Value	Meaning
Critical	0x3	Fail the attempted system startup
Severe	0x2	Switch to LastKnownGood or, if already using LastKnownGood, continue on in case of error
Normal	0x1	Continue startup if the driver fails to load, but display a message noting the failure
Ignore	0x0	—

If you want to change the dependencies for loading the service, specify new values under DependOnGroup, DependOnService, or Tag.
If you want to change when the service is started or the driver is loaded, change the Start value as follows:

Start type	Value	Meaning
Boot	0x0	Loaded by the Boot Loader
System	0x1	Loaded at Kernel initialization
Auto load	0x2	Loaded or started automatically at startup
Load on demand	0x3	Available, but started only by the user
Disabled	0x4	Not to be started under any conditions

Close Registry Editor, shut down, and restart the computer for these values to take effect.

For details about Start and ErrorControl values, see their definitions in "CurrentControlSet\Services Subkeys" in Chapter 14, "Registry Value Entries."

You can also set parameters for many drivers and services, as described in Chapter 14. For example, a modem that includes a National Semiconductor 16550 AUART chip can take advantage of FIFO buffer support. This capability is not turned on by default in Windows NT, however. If you are using such a modem, you can change the value of ForceFifoEnable to 1 to turn on FIFO support, under this subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet
\Services\Serial\Parameters