SQL Server Express
SQL Server 2005 Express Edition is the next version of MSDE and is a free, easy-to-use, lightweight, and embeddable version of SQL Server 2005.
Free to download, free to redistribute, free to embed, and easy for new developers to use immediately, SQL Server Express includes powerful features such as SQL Server Management Studio Express, for easily managing a database.
Get an overview of SQL Server Express, a free product based on SQL Server 2005 technology that includes the unique Application XCopy feature, and networking and security that differ from other SQL Server 2005 editions.
Discover what makes SQL Server Express Edition easier to use and protect, and more secure and stable than your existing JET applications.
SQL Server Express is freely redistributable once you've registered with Microsoft for redistribution rights.