nx 6110

hi

i have 2 laptop hp compaq nx6110, loaded with window XP pro, 512 RAM, 1.8GHz.

have this problem.
one display a line from left to right a white one when windows load and after a period it grows all over the screen

the second one, has a black line from top to bottom of the sreen but this one is black and it does not grow u.

what this could be?
and how am i going to solve this?

thanks.