Registry Settings for Windows Service

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MyService\Start

The type of "Start" is "REG_DWORD"

The value as follows(copied from MSDN):
0x0 (SERVICE_BOOT_START)
Indicates a driver started by the operating system loader.

This value must be used for drivers of devices required for loading the operating system.
0x1 (SERVICE_SYSTEM_START)
Indicates a driver started during operating system initialization.

This value should be used by PnP drivers that do device detection during initialization but are not required to load the system.

For example, a PnP driver that also can detect a legacy device should specify this value in its INF so that its DriverEntry routine will be called to find the legacy device, even if that device cannot be enumerated by the PnP manager.
0x2 (SERVICE_AUTO_START)
Indicates a driver started by the service control manager during system startup.

This value should never be used in the INF files for WDM or PnP device drivers.
0x3 (SERVICE_DEMAND_START)
Indicates a driver started on demand, either by the PnP manager when the corresponding device is enumerated or possibly by the service control manager in response to an explicit user demand for a non-PnP device.

This value should be used in the INF files for all WDM drivers of devices that are not required to load the system and for all PnP device drivers that are neither required to load the system nor engaged in device detection.
0x4 (SERVICE_DISABLED)
Indicates a driver that cannot be started.

This value can be used to temporarily disable the driver services for a device, but a device/driver cannot be installed if this value is specified in the service-install section of its INF file.