Login for multiple authentication systems

We have an app for use in medical surgeries and with CCHIT certification becoming a requirement, redefine our own safety. We've traditionally done our authentication / authorization at the login / password / access level, but while we have to rewrite to be standards compliant, why not be more flexible.

Although we are a Windows application, some of our clients do their authentication over UNIX, others use Novell, others use Windows Active Directory, others use nothing at all (small offices, small network). I would like to write against one server (or write one server) that we can use in ANY environment we are currently working in, which allows the client to use what they already created, rather than support two different inputs as they are now linked with our product.

Look for suggestions for an application that can be made to provide authentication work if it doesn't already exist, but will work with the authentication tool you're using if it exists.

Thanks.

And, if that matters, we work in Delphi, currently don't require .NET, and also know Java.