If you have old Christmas tree lights that no longer work, there are a few things you can do with them. You can recycle them at a local recycling center or a recycling facility that accepts electronic waste. You can also donate them to a local charity or non-profit organization that may be able to use them. You can also try to repair the lights by checking the wiring and replacing any damaged parts. If none of these options work, you can safely dispose of the lights in the trash.