I presume you are talking about SQL Server here. A backup file is a database file used by SQL Server. I think SQL Server is currently only way to read its contents in usable fashion.
I am unclear about your purpose of doing the task. I suspect you have database backup file and want to use the data without installing SQL Server. How about installing Free SQL Server Express Edition? Check out http://www.connectionstrings.com/sql-server-2005
], it will show you how to connect with a backup file.