I have replaced the battery in my 1992 Eldorado but still everytime i turn the car off either I wont have any battery power at all or when I try to start the car the battery completely drains. What can be the causing this?

You have a power drain! Check the light in the glove box, that can stay on if the switch is bad. From there you'll have to trouble shoot each circuit to see where the power draw is.