Nowhere in BartPE do I see any reference to ElTorito (and as Jaclaz explained, it doesn't apply anyway). If you really created a cd last year, you might remember that you did not use any ElTorito settings anywhere, so the answer is "none is enough". Once the ISO is created (if you use own burning software), just burn the ISO, not put the iso file on a cd, but burn "the iso image" to a cd. The iso IS a bootable CD ('s image) and that CD does not need any modification (like "making it" bootable by adding anything). If still unsure, tell us what burning software you are using and someone will tell you what menu to use.