SQL 2008 Express Editions and Service Packs -( from Microsoft site

Microsoft® SQL Server® 2008 Express with Advanced Services 

Microsoft® SQL Server® 2008 Express Edition Service Pack 1 

Microsoft SQL Server2008 R2 RTM - Express with Advanced Services 

Microsoft SQL Server 2008 SP2 Express Edition Service Pack 2 

SQL Server 2005 Backward Compatibility-1

SQL Server 2005 Backward Compatibility-2

(Click on the option for download page in Microsoft Site)