The power supply for my HP laptop has died. Its 19v 30w power supply . I have another power supply that is HP that is 18.5v and 80w will it hurt my laptop if I use it?

It should work fine. The fact that the power supply is rated for higher wattage simply means that it has the capability of driving devices that require more power than your lap top. Does the replacement supply have the appropriate connector to plug into your laptop?