SQL Server 2008 Error occurring when trying to attach database

Hi.

I'm trying to attach a database in Management Studio but am recieving an the following error. What can I do to resolve this? I'm using an Administrator account also.

===================================

Attach database failed for Server 'RW113L'.  (Microsoft.SqlServer.Smo)

------------------------------
For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=10.0.1600.22+((SQL_PreRelease).080709-1414+)&EvtSrc=Microsoft.SqlServer.Management.Smo.ExceptionTemplates.FailedOperationExceptionText&EvtID=Attach+database+Server&LinkId=20476

------------------------------
Program Location:

   at Microsoft.SqlServer.Management.Smo.Server.AttachDatabase(String name, StringCollection files)
   at Microsoft.SqlServer.Management.SqlManagerUI.AttachDatabaseData.PrimaryFile.Attach()
   at Microsoft.SqlServer.Management.SqlManagerUI.AttachDatabase.SendDataToServer()

===================================

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

------------------------------
Program Location:

   at Microsoft.SqlServer.Management.Common.ServerConnection.ExecuteNonQuery(String sqlCommand, ExecutionTypes executionType)
   at Microsoft.SqlServer.Management.Common.ServerConnection.ExecuteNonQuery(StringCollection sqlCommands, ExecutionTypes executionType)
   at Microsoft.SqlServer.Management.Smo.ExecutionManager.ExecuteNonQuery(StringCollection queries)
   at Microsoft.SqlServer.Management.Smo.Server.AttachDatabaseWorker(String name, StringCollection files, String owner, AttachOptions attachOptions)
   at Microsoft.SqlServer.Management.Smo.Server.AttachDatabase(String name, StringCollection files)

===================================

Unable to open the physical file "C:\Murach\SQL Server 2008\Databases\AP.mdf". Operating system error 5: "5(failed to retrieve text for this error. Reason: 15105)". (.Net SqlClient Data Provider)

------------------------------
For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=10.00.1600&EvtSrc=MSSQLServer&EvtID=5120&LinkId=20476

------------------------------
Server Name: RW113L
Error Number: 5120
Severity: 16
State: 101
Line Number: 1


------------------------------
Program Location:

   at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection)
   at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection)
   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj)
   at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)
   at System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async)
   at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(DbAsyncResult result, String methodName, Boolean sendToPipe)
   at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
   at Microsoft.SqlServer.Management.Common.ServerConnection.ExecuteNonQuery(String sqlCommand, ExecutionTypes executionType)