Well, what graphics card is it? That aside, for CS4 you needn't bother. OpenGL in older versions of AE is for all intents and purposes irrelevant.
Mylenium is correct. The OpenGL features (with the exception of the OpenGL - Interactive preview mode) weren't very useful in After Effects CS4.
Without furhter information about what your GPU is and what drivers you have installed, we can't help.