Longhorn and Biometrics, Bis
I checked a bit what I can find in Longhorn concerning that Biometric stuff. And I found that it is BAPI: bapi.dll, . That specification was bought some long time ago from i/o software and I remember that it was planned to have this integrated in Windows XP. I think that Microsoft did not included it because the biometric technology was not ready at that time.
I know a bit more about BioAPI than BAPI, but at the end I think it works almost the same. There is also a <strong><em>Kernel Biometric Service Provider</em></strong>: kbsp.dll and a tool called biotool.exe permiting to enroll a new biometric credential: