If your Mac runs slowly
Start up in Safe Mode
Steps 1 through 7
Reinstall OS X
i tried the first 2 steps , nothing changed .
later on i tried to reinstall the os but when it came to choose on which drive to install the os , it says S.M.A.R.T error and i need to back up and change hardisk since it cannot be repaired , should i change the hardisk or is there some other options ?