SQL Server 2005 Express Edition
SQL Server Express is a version of SQL Server 2005 designed for building simple, dynamic applications. SQL Server Express helps developers build robust and reliable applications by providing a powerful database that is also free and easy to use.



http://lab.msdn.microsoft.com/express/sql/default.aspx
Too often database systems are overly complex for building simple applications. SQL Server Express and the other Express products reduce this complexity by providing a simple but powerful development environment for building data-driven applications. You can design schemas, add data, and query local databases, all inside the Visual Studio 2005 environment. If you need more advanced database features, then SQL Server Express can be seamlessly upgraded to more sophisticated versions of SQL Server.
Comparison of MSDE with SQL Server Express
SQL Server Express 2005 MSDE 2000 Application XCopy support Feature not present No DTS DTS runtime present Easy deployment because of no MDAC MDAC is part of install MSI only, good servicing story MSI and MSM, servicing of MSM hard Client Replication for Transactional, Merge, and snapshot Merge/snapshot publication supported in addition to replication subscription Robust Setup UI Basic setup UI No agent Agent present Supports Windows 2000 SP4, Windows XP SP1, and Windows 2003 Supports Windows 98, Windows Me, Windows 2000, Windows XP, Windows NT4, and Windows 2003 CLR support No CLR support GUI tools provided No GUI tools Database size limit: 4G Database size limit: 2G 1 CPU, 1GB RAM 2 CPU, 2GB RAM No throttle Workload throttle enforced Deep integration with Visual Studio Basic integration with Visual Studio








