ALTER DATABASE TempDB
ADD FILE(NAME = tempdb2, FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL10_50.MSSQLSERVER\MSSQL\DATA\tempdb2.ndf', SIZE =256)
ALTER DATABASE TempDB
ADD FILE(NAME = tempdb3, FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL10_50.MSSQLSERVER\MSSQL\DATA\tempdb3.ndf', SIZE =256)
ALTER DATABASE TempDB
ADD FILE(NAME = tempdb4, FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL10_50.MSSQLSERVER\MSSQL\DATA\tempdb4.ndf', SIZE =256)