What is the best setting to have my Nikon P100 on when shooting moving horses?

I'm not familiar with the settings on the Nikon P100, but I'll tell you what I do when I take photos at shows. The setting really depends on the lighting conditions. If the sun is out and there are very few clouds in the sky, I put my camera on manual after I find the correct exposure. Unless the lighting conditions change, I just leave it on that same setting throughout most of the show. I set the aperture to around 4.0, which gives the best results for my lens, set the ISO around 200, and change the shutter speed until I have a good exposure. For cloudy days, I just leave the ISO between 200 and 400 and then set the camera to aperture priority with the white balance set to cloudy. There really is no one setting to use when taking pictures at shows. Just mess around with a whole bunch until you find the one that gives you the best results. You can also experiment by setting the aperture as small as it can go (ex. 32) and reducing the shutter speed to get panning shots.