I have been advised to download cuda and I downloaded nvidia cuda version 6.5,yet the cycle compute showed none. what should I do? Help me please. I'm using windows 7 im trying to enable graphics card nvidia geforce 320
Don't waste your time, your card is too old, it is not supported by blender. As stated in the link
Cycles only supports CUDA GPUs with a CUDA compute ability of 2.0 or higher. To use CUDA, check to make sure your GPU is on this list of CUDA capable GPUs and has a ranking of at least 2.0.
Your's doesn't meet that criteria. You can see the compute capability of CUDA cards here: https://en.wikipedia.org/wiki/CUDA