Upgrade from SQL Express 2005 to 2008
If you have a SQL Express 2005 installation with Sql Management Studio express installed these four commands will do a silent upgrade to 2008.
First extract the contents of the SQL Express download into a directory.
SQLEXPRWT_x86 /EXTRACT
Install Windows Installer 4.5 and Windows Powershell.
Then remove SQL Tools 2005
msiexec /quiet /Uninstall {58D379F7-62BC-4748-8237-FE071ECE797C}
Remove Management Studio
msiexec /quiet /Uninstall {20608BFA-6068-48FE-A410-400F2A124c27}
Ugrade the SQL Engine.
SETUP.EXE /QUIET /ACTION=upgrade /INSTANCENAME=SQLExpress
Install Management Studio 2008 Express
SETUP.EXE /QUIET /ACTION=Install /FEATURES=Tools /INSTANCENAME=SQLExpress