1-Enable .NET3.5 from the command line using the following command

 Dism.exe /online /enable-feature /featurename:NetFX3 /All

2-Download SQL server 2008 service pack 3 from

 http://www.microsoft.com/en-us/download/details.aspx?id=27594 

3-Double click on package exe to install SQL 2008 latest SQL support package that supports slipstream installation.

4-Extract SQLServer2008SP3-KB2546951-x64-ENU by running the below command from command line

SQLServer2008SP3-KB2546951-x64-ENU /x:”c:\SQLSERVER2008SP3″

5-Command line to install SQL server 2008 + Service pack 3

setup.exe /Action=Install /q /InstanceName=<InstanceName>

/FEATURES=SQLEngine,FullText,AS,RS,IS,Tools /AGTSVCACCOUNT=”<DomainOrMachine\User>” /AGTSVCPASSWORD=”<DomainOrMachineUserPWD>”

/ASSVCACCOUNT=”<DomainOrMachine\User>” /ASSVCPASSWORD=”<DomainOrMachineUserPWD>” /RSSVCACCOUNT=”<DomainOrMachine\User>” /RSSVCPASSWORD=”<DomainOrMachineUserPWD>”

/SQLSVCACCOUNT=”<DomainOrMachine\User>” /SQLSVCPASSWORD=”<DomainOrMachineUserPWD>” /SQLSYSADMINACCOUNTS=”BUILTIN\Administrators” /ASSYSADMINACCOUNTS=”BUILTIN\Administrators” /pcusource=”c:\SQLSERVER2008SP3″

/pid=<PID key for edition>

Same installation can run in UI mode be removing the /q switch