How do I fix a wooden floor board?

I have this plank of wood on my wooden floor that has gotten pretty bad. The wood around it is in okay condition, so I dont want to have to change the entire floor. Is there a way I can change that plank, so that it doesn’t look so bad?

Here is a picture of it: http://www.flickr.com/photos/51126462@N04/4697117329/