>>550
FIX: Error message when you connect to a 64-bit instance of SQL Server Express 2008
by using Visual Studio 2008 Service Pack 1 (SP1):
"Connections to SQL Server files (*.mdf) require SQL Server Express 2005 to function properly"
http://support.microsoft.com/kb/957944/en-us

Solverlight 3.0 のやつを入れればファイルは新しくなると思うんで
それでいけるかと。

Visual Studio 2008 SP1 用 MicrosoftR Silverlight? 3 Tools
http://www.microsoft.com/downloads/details.aspx?FamilyID=9442b0f2-7465-417a-88f3-5e7b5409e9dd&DisplayLang=ja