Do you mean you have you downloaded the crack from here:
http://dl.gamecopyworld.com/?d=2006&f=rld-s2pe!rar
but when you try to unrar it into the game directory the 'Sims2EP4.exe' is write protected and you cannot copy over the crack?
If so, right click on the 'Sims2EP4.exe' in your game directory and click the 'Properties' button, then find and untick the box that says 'Read-only' and then click the 'Apply' button and then 'OK' to remove that attribute. You should then be able to copy over the crack.