If you are trying to restore database backup of SQL Server 2008 to SQL Server 2005, you are bound to fail. Database backup of SQL Server 2008 is not compatible backward, you cannot restore it to SQL Server 2005. The following is a solution to convert databases of SQL Server 2008 to 2005
Open SQL Server Management Studio2008. in 'Object Explorer', right click the database that you want to convert. Select 'Tasks' > 'Generate Scripts...'.
Click 'Next'.
Select the database that you want to convert, and check on 'Scripts all objects in the selected databases'
Set options:
'Script for Server Version' = 'SQL Server 2005' 'Script Data' = 'True' 'Scirpt Database Create' = 'True'
Select option 'Script to file', 'Single file' and 'Unicode text'.
View summary and click 'Finish'.
CREATE DATABASE [StockTraderDB] ON PRIMARY ( NAME = N'StockTraderDB', FILENAME = N'c:\Program Files\Microsoft SQL Server\MSSQL10.SQLEXPRESS\MSSQL\DATA\StockTraderDB.mdf , SIZE = 4352KB , MAXSIZE = UNLIMITED, FILEGROWTH = 1024KB ) LOG ON ( NAME = N'StockTraderDB_log', FILENAME = N'c:\Program Files\Microsoft SQL Server\MSSQL10.SQLEXPRESS\MSSQL\DATA\StockTraderDB_log.LDF', SIZE = 6272KB , MAXSIZE = 2048GB , FILEGROWTH = 10%)
When finished, You should get converted database of SQL Server 2005