HKLM\SYSTEM\CurrentControlSet\Services\RemoteAccess\Authentication\
The Authentication\Providers subkey stores configuration data for Routing and Remote Access authentication providers, such as Windows and RADIUS.
The Providers subkey contains entries that apply to all dial-up authentication providers. It also contains subkeys representing each provider, which are named by the GUID of the provider and store entries that apply only to that provider.
The following authentication providers are included in Windows 2000
Related Entries
{1AA7F83F-C7F5-11D0-A376-00C04FC9DA04} (RADIUS authentication provider subkey)
{1AA7F841-C7F5-11D0-A376-00C04FC9DA04} (Windows authentication provider subkey)
{1AA7F840-C7F5-11D0-A376-00C04FC9DA04} (RADIUS accounting provider subkey)