In a medium saucepan combine water, sugar, lemon juice, and ginger. Bring to boiling. Remove from heat; add frozen peaches. Let stand about 30 minutes or until peaches are thawed and mixture has cooled.
Add peach mixture, half at a time, to a blender container. Cover and blend until smooth. Transfer blended mixture to a 2-quart rectangular baking dish. Cover and freeze for 3 to 4 hours. Break up mixture with a fork; spoon into dessert dishes. Top with fresh peach slices. Makes 8 (1/2-cup) servings.