back up from .bak file

I got a .bak file from my friend
I want to restore the data base (presently I don’t have any database in my system).

But while I try to restore it
I am getting an error

“
System.Data.SqlClient.SqlError: Directory lookup for the file "D:\Microsoft SQL Server 2005\mydatabase.mdf" failed with the operating system error 2(The system cannot find the file specified.). (Microsoft.SqlServer.Smo)

”

I have installed Microsoft sql server in a different directory
Not where he is installed

I can successfully restore the back up files of data base on my own system
But not the backup files created from others systemsWhen you restore the backup, there is a place on the dialog that will list all of the assoicated files for the backup and where they should be placed (.mdf, .ldf, etc.) The paths will default to the location that they were backed up from. You need to change these paths to where you want the files placed.