users with hardware problems

Just to point out: I'm very new at this.
I just started and I need help, big time:
Whenever i play Dark Forces2 the modded levels have strange graphic effects, such as when i look away from a wall the floor cuts away.
In that one you have to look directly at something to see it.
I think it was in Edward's Jedi Arena, or some thing like that.
Another thing i don't understand is when i look at certain walls in the 420 Lounge, the image drags along. If i didn't make that one clear, ill try:
you fire at the wall, the blast 'stays' there until you move, then everything blurs around you. If anyone can help me get this cleared up, please post some helpful words of advice. Much obliged.