How to have Secure local Data Base C# application

I have a C# application with .NET 3.5 and SQL SERVER 2008 R2. I want to make a setup project and i want to install each user db while installation.

I use local db when i import database as application file, the database is available and anyone who has access to the laptop os has access to the database. because the local db' s are not for the multiuser scenarios.

how to secure the database file' s from access or being modified? it contains sensitive data for application behave.