Offline Database storage

I am writing a program that will reside on a users computer and is for the home user who would not likely have an SQL server in their home. I want to know a way to store information on the clients machine without installing a database engine such as MSDE. I guess I could use disconnected DataSets but, I don't want to save the data in XML, as the user could view and change using notepad. I have heard about ADTG files. How do I save to this Microsoft format?

How do programs normally do this? Binary files, text files....? I normally create programs with access to a database server. This is my first attempt at one that won't

I don't know whether this would be useful to you but you might think about using the XML solution and then encrypting the XML file. I don't know about ADTG files so I don't know which would be easier, but the encryption option shouldn't be too difficult.

There is also the possibility of using an Access database. You don't need to have Access installed to use an MDB file and there are some measures you can take to secure the file. You'd need to write code separate to that that's used for SQL Server, but it would be virtually the same. You would just be using System.Data.OleDb instead of System.Data.SqlClient.