What is this burnt thing?

While moving from a nr200 to a new ap201 (I finally have some more desk space) I noticed this burnt part in the back of the motherboard.

I remember the first time I tuned it on that it sparked but continued to work perfectly for the two years I have had it. Y had my CPU undervolted so I guess it never consumed too much energy to make a difference but yeah guess I'll ride it until I have more money to also change it into an matx for more ram slots.