What pre/post are you using. Are you looking at a meshed model or just geometry? Most of this software has extensive help sections on setting up graphics for cases like yours. Have you consulted these? My first advice is to spend the money on a better graphics card. Your question is nebulous, so not being sure what state the model is in when you are having problems, create layers or groups that you can turn on/off to view just those sections of the model you are currently working with. Turn off nodes, points etc. that you don't need to see (could be grouped again). See if you can stop items from being displayed during dynamic rotation via software preferences. The list goes on and on, but again, your render graphics section of the program help file should lead you in the right direction...
rjw57