few questions

1-my pentium 2 hangs up frequently.
2-when I leave computer unattended say for 1 hour,it stops responding. .
3-My video card has been changed, when i boot my computer there is messsage
in different colors 'real 3D starfighter VGA Bios' is it something about
video card.
4- sometimes some programs or even desktop display appears shortened
vertically( almost to 1/2 ) as if watching cinema scope movie on TV screen
5-Faint lines keep on appearing on screen and screen seem to be somewhat
flickering.
..please help