"Failed to Bind Port" Minecraft Server

You posted seven hours ago, so the immediate problem may have been resolved by the reboot suggested in another answer. However, as a more fine-tuned solution, you might find this answer valuable: How to close TCP and UDP ports via windows command line.

Rebooting the entire machine will end all processes, freeing all ports used by those processes, and that includes the 'defunct' Minecraft server process using 255656. However, if you end that process itself (and any of its children), you will be able to free the port it used.

Minecraft is a good practice environment for many skills you can use later. If you ever want to run a server in a work environment, you'll want to avoid rebooting it unless absolutely necessary, so practising the more precise fix is valuable.

Pretend we have a sheet of paper with lots of holes. Those holes are ports.

Minecraft wants to use Port Number 25565. You allow it. So you stick a pin through that hole.

When you shut a server down properly, it tells the hole to disconnect Minecraft's pin from the ports. When you don't, the server is no longer online, but the pin's still connected. (For absolutely no reason)

The simple fix, is to restart your computer, ultimately disconnecting all used ports, refreshing it so you can simply get back to whatever you were doing when the computer turns back on...

Don't worry, this happens to everyone at one stage in their server hosting lifetime.

A currently running process is listening on port 25565 and will not give it up to the new instance of your server.

In your situation, it's likely the process that's "clogging" the port is (part of) a previous instance of your server that wasn't shut down properly.

In Windows XP, run the command prompt with Win+R>cmd. Then run the command netstat -ano to list all active connections. Find the entry whose "Local Address" is using the target port (ie: 0.0.0.0:25565) and see the PID listed on that line. That is the Process ID for the process listening/connected on that port currently. Killing that process will make the port available again.

There are a few ways to kill a process. Since we're already on the command line, I would simply type taskkill /PID %PID%, where %PID% is the PID value you obtained from netstat.