Photoshop doesn't use the GPU, (except for the opt-in GPU mode, which is slower than CPU). You won't see any speed boosts in Photoshop.
Maybe under Lightroom.
From Abobe's website "Photoshop CS5 and CS4 leverage the graphics display card's GPU, instead of the computer CPU, to speed its screen redraw. For Photoshop to access the GPU, your display card must contain a GPU that supports OpenGL and has enough RAM to support Photoshop's functions - at least 128 MB, and a display driver that supports OpenGL 2.0 and Shader Model 3.0.
Are these the functions that run slower?
Not really, but you should upgrade your card anyway. The 8800 is a POS