The Serial subkey stores default settings for all serial ports on the computer. Settings for a specific serial port can be overridden by the values of entries in the Enum subkey for that device.
In Windows NT 4.0 and earlier, the Serial\Parameters subkey contained Serial# subkeys, which stored settings for individual serial ports. In Windows 2000, settings for individual ports are stored in device-specific subkeys of the Enum subkey. If you have upgraded from Windows NT 4.0 and earlier, Serial# subkeys might remain in your registry, but they are not fully supported. For more information, see Serial# subkeys.
To override the values of entries in the Serial subkey for any specific device, use Device Manager.