CautionHKLM\SYSTEM\CurrentControlSet\Services\Serial\
The Parameters subkey appears in the registry to provide compatibility with Windows NT 4.0 and earlier.
In Windows NT 4.0 and earlier, the Serial\Parameters subkey contained Serial# subkeys that stored settings for individual serial ports. For Windows 2000, settings for individual ports are stored in device-specific subkeys of the Enum subkey (HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum). If you have upgraded from Windows NT 4.0 or earlier, Serial# subkeys might still appear in your registry, but they are not fully supported. For more information, see Serial# subkeys.
Caution
Do not edit the Serial# subkeys in Parameters. To configure individual serial ports in Windows 2000, use Device Manager. Device Manager can associate each port with the correct device-specific subkey in Enum and changes its settings accurately.