>>What is your and clients SQL Server versions? Backups are not backward compatible.
>>
>>>A client sent me a database (.bak) file. I'm trying to restore it. I'm getting
>>
>>>TITLE: Microsoft SQL Server Management Studio
>>>------------------------------
>>>
>>>An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo)
>>>
>>>------------------------------
>>>ADDITIONAL INFORMATION:
>>>
>>>The media family on device 'C:\Program Files (x86)\Microsoft SQL Server\MSSQL.1\MSSQL\Backup\ER_VT_backup_2011_05_10_020001_3850000.bak' is incorrectly formed. SQL Server cannot process this media family.
>>>RESTORE HEADERONLY is terminating abnormally. (Microsoft SQL Server, Error: 3241)
>>>
>>>For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=09.00.5000&EvtSrc=MSSQLServer&EvtID=3241&LinkId=20476
>>>
>There will be a different error message if this is a version compatibility problem.


What if the backup is created with compression and you don't have Enterprise version?