The ODBC API provides ways to enumerate both DSN (Data Sources)
and ODBC Drivers, and it's actually pretty easy to do once you know where to
look. Here's a sample that shows User and System DSNs installed on the system,
as well as available drivers. It's a full MFC application,but it's pretty
simple, and it's UI is pretty simmilar to the ODBC configuration control panel
applet. The App is written in VC++ 6.0, but should be easy to move to 5.0.

a plus, the sample shows how to use a CPropertySheet as the app's main window
(instead of a dialog), and how to use parent classes based on MFC to add more
code reusability, while keeping the ability to use ClassWizard to add message

Now, download the files from here