i have a cannon and a kodak, can i use both on same disc, or do i need to install both discs?

You don't need to install either one, really, to use both cameras, unless there's features on the software that you want. In fact, I recommend an external card reader, so you can just pull the memory card out of the camera and insert it into the card reader--saving your camera's battery power.

When you install a card reader or plug a camera in, it should see the camera or reader as a mass storage compliant device--essentially an external removable drive. Thus, you should see it as a new drive letter on your "my computer" folder. From there you can copy the images and open them.

The software is just to do things like fix redeye, resize, etc. Pick one and install that. You don't need to install both of them, unless there's features on both that you like or because you need to control the cameras via the computer somehow.

Those are 2 different brands. Each has it's own unique drivers, etc. You will have to install the software for each.