SQL Server Compact 4.0
Embedded Database for Building Client Applications

I have seen many questions floating around on C# Corner and
other forums developers asking about Access database or SQL Server Express
database to provide embedded database support for small applications.
My answer is simple, SQL Server Compact 4.0. Forget MS-Access
and forget SQL Server Express, check out SQL Server Compact 4.0.
Microsoft SQL Server Compact is a free SQL Server embedded
database ideal for building standalone and occasionally connected applications
for mobile devices, desktops, and Web clients.
Top Features
- Free to use and distribute
- Supports desktops and mobile devices
- Small footprint for easy deployment
- Fully embeddable architecture
- No administration required
- Single file, code-free database format
- Support for ClickOnce, XCopy, MSI, CAB, and non-admin
embedded installation options
- Supports all Microsoft Windows embedded, mobile, desktop,
and server operating systems
- Supports a rich subset of Transact-SQL syntax and SQL Server
data types
- Microsoft Visual Studio 2008 integration
- Supports ADO.NET, LINQ to SQL, LINQ to Entities, and the
ADO.NET Entity Framework
- Supports multiple concurrent local connections
Download Microsoft SQL Server Compact 4.0 here: http://www.microsoft.com/download/en/details.aspx?id=17876