Using Win7 Pro, I've got several .mdf's that were originally created as part of an ASP.NET application in SQL Server Express 2005, under VS2005.
I upgraded to VS2012, and to SQL Server 2012 EXPRESS. The instance of SQL running on my machine now is MSSQL11.SQLEXPRESS / 11.0.2218 RTM.
During the upgrade, I did nothing to the the .mdf files.
The application works fine under VS2012 and SQL 2012 Express; there was very little code or configuration file change required.
I can open the .mdf's using the Server function in either VS2012 or VS2010 Shell, run queries, update the tables, modify/add tables, etc.
However, when I try to attach any of these .mdf's using MSSMS (this version)
Microsoft SQL Server Management Studio	11.0.2100.60
Microsoft Data Access Components (MDAC)	6.1.7601.17514
Microsoft MSXML						3.0 4.0 6.0
Microsoft Internet Explorer				9.10.9200.16686
Microsoft .NET Framework				4.0.30319.18052
Operating System						6.1.7601
I get "Error occurred while attaching..... Click on hyperlink in message column" but there's no hyperlink in the message column.
Any suggestions on what to do about this would be appreciated.