After I downloaded "minecraft_server.1.7.10.exe" and launched it (I set it up too), I changed the world it generated with one of my worlds from my ".minecraft". I then renamed it to "world" and then launched the server. When I open multiplayer in minecraft it just says "Old" and then after about 10-15 seconds the Minecraft Server closes. when i take out my world and let it generate its own it works fine. Please Help