Buy an internal drive, straight swop for the drive that you got in now.
Go for internal dvdrw cdrw dvdrom the works, youll get one in argos for £40 quid, its as easy as changing a lightbulb.
Just take the old drive out, remembering where the wires went theres 1 power connector and 1 ribbon connector, theres only one way to put the wires and put the new one in the same place.