Cook pasta according to the package directions, omitting salt and fat. Drain in a colander over a bowl, reserving 3 tablespoons cooking liquid.
Heat pan over medium heat. Coat pan with cooking spray. Add garlic to pan, and sauté 1 minute. Remove from heat. Add reserved 3 tablespoons cooking liquid and pasta to pan; let stand 2 minutes. Stir in parsley, oil, salt, pepper, and prosciutto; sprinkle with cheese. Serve immediately.