Error 5120

This is my issue that I am faced with in using sql with ms windows vista operating system. Please help this is hindering my progress.

TITLE: Microsoft SQL Server Management Studio Express
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Attach database failed for Server 'XXXXXXX\SQLEXPRESS'.  (Microsoft.SqlServer.Express.Smo)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=9.00.3042.00&EvtSrc=Microsoft.SqlServer.Management.Smo.ExceptionTemplates.FailedOperationExceptionText&EvtID=Attach+database+Server&LinkId=20476

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ADDITIONAL INFORMATION:

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

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Unable to open the physical file "C:\Ch07_AviaCo\Ch07_AviaCo_Data.mdf". Operating system error 5: "5(Access is denied.)". (Microsoft SQL Server, Error: 5120)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=09.00.3042&EvtSrc=MSSQLServer&EvtID=5120&LinkId=20476

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BUTTONS:

OK
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