standalone database

I'm working on an app that is basically a ui and a database.  How should I implement the database?

For the sake of the argument pretend it's for an iTunes/Foobar type music player.

inb4 no help at all

>>3
Just for even considering the use of XML for a database, you now must repeatedly bludgeon yourself with a Data Structures and Algorithms textbook. Make sure to use one that's at least 500 pages.