>Does anyone know of an API or a way I can authenticate a user into a VFP application using kerberos?
>

I've never used them, but both CAPI and SSPI have some support for Keberos, as does DirectPlay4 (you'll probably need to write wrappers for it, since I'm only aware of a C++ interface for SSPI). Since Kerberos is integral to NT 5/Win2K, I'd expect to see some COM-based support available somewhere. There are a couple of white papers that discuss integration of Kerberos into the NT environment as a replacement for NTLM authentication at a very surface level (frankly, as far as I have pursued it); Secure Networking Using Microsoft Windows NT 5.0 Distributed Security Services is available on MSDN, as are the Crypto API Appendices.

CAPI is part of the Platform SDK, and can be downloaded from MSDN OnLine. There is no sample VFP code. If you don't want to write wrappers on the API calls in another language like C, you'll need to use something like POINTERS, which provides an OLE interface to work with structures, or my CLSHEAP, which provides a class for manipulating heap block memory allocations, and some useful procedure wrappers on API calls to read from and write to blocks of memory not managed by VFP directly.