Pierce potatoes several times with fork. Place on microwavable paper towel in microwave oven. Microwave on High 10 to 13 minutes or until tender, turning potatoes over and rearranging halfway through cooking. Let stand in microwave oven 5 minutes.
Meanwhile, in 10-inch nonstick skillet, cook ground beef over medium-high heat 5 to 7 minutes, stirring frequently, until thoroughly cooked; drain if necessary. Stir in 1/2 cup salsa and the chili powder.
Cut potatoes in half lengthwise; place 2 halves on each plate. Spoon beef mixture evenly over potatoes. Sprinkle 1/4 cup cheese over each serving. Serve with sour cream and additional salsa.