If you have a microwave oven that is no longer working, you will want to dispose of it safely. Here are a couple of ways to do it: contact your local refuse company and ask if they will dispose of it for you. If not, you might be able to find a local appliance repair shop who will be glad to take it off your hands; they might be able to get it working again or retain working spare parts.
In order to dispose of a microwave you would need to check your local laws. Another option is to contact U.S. Environmental Protection Agency for more information about where you can dump your old microwave.