Download SQL server 2008 service pack 3
http://www.microsoft.com/en-us/download/details.aspx?id=27594
Extract SQLServer2008SP3-KB2546951-x64-ENU by running the below command from command line
SQLServer2008SP3-KB2546951-x64-ENU /x:”c:SQLSERVER2008SP3″
Run the Setup.exe file from the SQL Server 2008 source media by specifying the /PCUSource parameter. For example:
Setup.exe /PCUSource=C:SP1
https://support.microsoft.com/en-us/kb/955392