one Thing I found out: Windows 7 produces a memory leak while using certain methods to access rendertargets. Why doesn't Windows 8 leak at this method?

 public class Game : SharpDX.Toolkit.Game {
 	GraphicsDeviceManager gdm;
 	RenderTarget2D target;
 	public Game() {
 		gdm = new GraphicsDeviceManager(this);
 	}
 	protected override void LoadContent() {
 		target = RenderTarget2D.New(GraphicsDevice, 1000, 1000, PixelFormat.R8G8B8A8.UNorm);
 		base.LoadContent();
 	}
 	private Color GetColor(int x, int y) {
 		using (Image image = target.GetDataAsImage()) {
 			PixelBuffer buffer = image.PixelBuffer[0];
 			Color color = buffer.GetPixel<Color>(x, y);
 			buffer = null;
 			return color;
 		}
 	}
 	protected override void Update(GameTime gameTime) {
 		GetColor(5, 5);
 		base.Update(gameTime);
 	}
 }

The memory consumption with this on Windows 8 is around 25 MB, Windows 7 uses up full memory.
Any idea why Windows 8 handles memory/graphics in another way than Windows 7 (and how to fix it)?