The graphics card does not matter with AE. At all.
What are the specs of your comp? What were your render settings? What are your memory and multiprocessing settings?
Let's cut to the point, shall we?: You have enabled MP rendering (Render Multiple Frames Simultanously) most likely and due to your inexperience you use the "dumb" default settings and it's completely whacking out your system, since you don't have enough RAM vs. the number of cores involved. Therefore please read the relevant help sections first. Also, depending on your settings, CoDecs and effects could be involved that are not MP safe and degrade performance, but without knowing teh exact specs, that's impossible to tell...
You must provide informaiton about the size of your project, the nature of the elements and effects you are using and the target render settings.
Rendering to DV from small items with simple effects is one thing; rendering to H.264 using particles generated form HD-sized elements in 3D with ten lights is an antirely different situation.
As the others have said, there's quite a bit more information that we need before we can effectively help you.
Here's a good place to start reading for memory and performance issues: