As far as i know, nvidea or ati cards shouldnt make a difference to your performance when your not using 3d graphics. They are basically 2 cards in one. When you open a program that needs to use the accelerator it switches over and the gpu handles as much of the work as it can and leaves the rest to your cpu. When working in standard windows it shouldnt make a difference on your performance at all. In most cases things like this will be caused by either a cpu top out or your ram cant handle it. Maybe its bad ram. Download cool beans system info - http://www.coolbeans.ws/sysinfo.shtml and see what your system perfomance is reading when you open these vst's that cause a problem.