MacBook Pro 2.3 ghz 2003 start up problems can it be fixed and if so what is it ?

Can anyone advise pls as my 2003 MacBook has been having start up problems and the screen has started to improve slightly from a few days ago going black and white zig zags but now gets to normal front page grey/blue and can use Mozilla one window then starts to go green diagonal zig zags .... help anyone ? Should I replace hand drive it is already running on one fan and gets very hot underneath too hot to have on your lap thanks