THIS VIDEO WILL HELPFUL IN INSTALLING SQL SERVER USING COMMAND PROMPT. A REAL TIME EXPLANATION.
COMMAND FOR UNINSTALLING SQL SERVER 2008
OPEN THE COMMAND PROMPT IN RUN AS ADMIN MODE AND THE RUN THE BELOW COMMAND
setup.exe /ACTION="unInstall" /QS /FEATURES=SQLENGINE,REPLICATION,FULLTEXT,CONN,BC,SDK,
BOL,SSMS,ADV_SSMS,BROWSER,WRITER /INSTANCENAME="NAME OF THE INSTNACE"