Transferring Pictures from Digital Camera to

Hello,

I am trying to transfer pictures I just took with my friend's digital camera to my PC. I connected the camera with the USB cable to my computer and the camera was detected. It started telling me to install a driver. I don't have the CD. I tried to download software for the Nikon ISO800 from dowload.com. It states that it is downloaded but how do I use it? When I tr to open it it is asking me what program to use to open it with. I don't know? I need help. I don't even know if I downloaded the right software to begin with. HELP!!