That folder holds a crucial part of the Registry - the great big filing cabinet in which Microsoft stores al the information about your system. You will need a CD but a borrowed one will do - it's not for installation, just for repair purposes but it will have to match the system you have - XP Home to Home or Pro for Pro. When you have it, please post back for step by step instructions as to how to see if there's a recent backup of that file and if so, how to replace it with that backup.