Multiple Parallel GPUs

Hi all,
I am using CUBLAS library to solve a large system of linear equations on single GPU. But I want to work with 2 GPUs in parallel. I have some questions and I really appreciate you if you help me:
First of all, I know that I must disable the SLI, but I don’t know how! I searched in the NVIDIA control panel but it is not there! (my GPUs are gtx280)
Second, I found the simpleMUltiGPU example in the nvidia’s projects, but it is for using pure CUDA; however, I am using cpp+CUDA, i.e. CUBLAS. Do you believe that in CUBLAS it is possible to use multiple GPUs too?
Thank you.

I forgot to say that I am using windows XP.