There's a couple of posts related to connecting to a Firebird database from an asp.net 2008 web application that are helpful but not complete.
First, you establish a DSN connection.
When adding the DSN connection the prompts were a little different on my Vista machine than the post describes. First, I picked the Database source
Then, after clicking New Connection button, click Change button on Data Source to switch from SQL Server to ODBC driver
Then, pick the Microsoft ODBC Data Source option
Once this is done when you add a new DSN connection the Firebird/Interbase drivers will be selectable.
During the configuration of the Firebird DSN connection I ran into one other change from the earlier post, rather than browse to the database on the local machine I used the localhost: connection method (e.g. Database = "localhost:c:\program files\ ... \_WEBLINK.FDB")
The Database string is quoted on both ends, in the picture some of the connection string is whited out for (excessive) security.
Now you can follow the second post to establish a data connection