SQL Server database restore error

I am trying to restore a database on SQL Server 2005 but when I try to select the backuo location, I get the permissions error:

TITLE: Locate Backup File - SPARROW-VAIO\SQLEXPRESS05

C:\Program Files (x86)\Microsoft SQL Server\MSSQL.2\MSSQL\Backup

Cannot access the specified path or file on the server. Verify that you have the necessary security privileges and that the path or file exists.

If you know that the service account can access a specific file, type in the full path for the file in the File Name control in the Locate dialog box.

I am using SQL Server 2008 R2 Management Studio and login to Sql Server 2005 using windows authentication. I tried to create a user and when I go to user mapping, and tried to give access to model database, it says database not available. My SQL Server 2005 version is

Microsoft SQL Server 2005 - 9.00.1399.06 (Intel X86)   
Oct 14 2005 00:33:37   
Copyright (c) 1988-2005 Microsoft Corporation  开发者_StackOverflow社区
Express Edition on Windows NT 6.1 (Build 7600: )

Please suggest solution.

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the issue fixed when I run SQL server 2008 R2 as Administrator