Attach the same .mdf to SS 2012 Express

Hi,
I detach the relevant DB schema within SS 2012 standard, and then attach it to SS 2012 express. But I get this

TITLE: Microsoft SQL Server Management Studio
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Failed to retrieve data for this request. (Microsoft.SqlServer.Management.Sdk.Sfc)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft%20SQL%20Server&LinkId=20476

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ADDITIONAL INFORMATION:

An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo)

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CREATE FILE encountered operating system error 5(Access is denied.) while attempting to open or create the physical file 'C:\Program Files\Microsoft SQL Server\MSSQL11.SS20122EXPR\MSSQL\DATA\my_schema.mdf'. (Microsoft SQL Server, Error: 5123)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft%20SQL%20Server&ProdVer=11.00.2100&EvtSrc=MSSQLServer&EvtID=5123&LinkId=20476

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BUTTONS:

OK
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is this way disallowed?

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Many Thanks & Best Regards, Hua Min