Does Video Encoding speed up if i have a better graphics card?

If I need to encode a video in Windows (32 and 64 bit) Vista, will it speed up automatically if I have a better graphics card or does the encoding use the CPU only, or does it also depend on things like drivers and the specific program being used for the graphics.( Will certain programs take advantage of a better graphics card while others won't) My computer has more than enough RAM.