Well since you install CUDA then you need to use a CUDA based miner. I have no idea if Guiminer used Cuda or not, but I'm pretty sure Ufasoft does.
Also according to the Mining hardware comparison chart it will hash slower than your CPU.
https://en.bitcoin.it/wiki/Mining_hardware_comparisonGood Luck and have fun,
Sam
Edit: OpenCL is for AMD GPU's by the way.