[strike]I am assuming you mean lines on the screen? If that is the case,[/strike] Try connecting an external monitor and see if it also shows the lines.
If it doesn't, then the attached display, or the cable that connects it, are the problem and need to be either repaired or replaced.
However, should the lines also show on the external monitor, then you are talking a GPU problem, and it may well need replacing, which could mean replacing the motherboard.