My laptop has started crashing quite frequently, the screen just freezes + no mouse/keyboard response - I have also noticed when it does so, that putting pressure on most areas of the underside cover causes some coloured lines to appear on the screen. It also seems to be fairly sluggish and 'glitchy' the rest of the time as well. I haven't made significant changes to it recently, and the windows 'check disc for errors' couldn't find anything wrong. It's quite old I have to admit (c.5yrs). What could be the cause of the crashes and how might I fix it? Thanks very much in advance