Not-so-good Smoke/Dust and Scenery

Hi, I'm new to this site and the world of simulation add-ons. I'm having a problem with the engine start-up smoke and impact dust/dirt/smoke if (when!) I crash, it ends up looking like huge spiraling squares. Trees and distant lights will also become encased in big black squares. This only happens when I've installed one particular aircraft or another, the first couple are ok, then one will screw up the graphics and I end up dumping all of FS 2002 Pro and re-installing, vowing to never download anything again...which I really can't see doing. Hope someone can help...Thanks!
system- Athlon 1200, 3DForce4 Ti 4200 8x, 512mb
system- Athlon 1200, 3DForce4 Ti 4200 8x, 512mb