CopyFromScreen not capturing entire desktop on Windows 8

I am developing an application for Windows 7 and thinking about migrating to Windows 8. The problem is that when using CopyFromScreen for my screen capture operation, I'm noticing it does not capture the entire desktop on Windows 8 (only the top-left quadrant). It works perfectly on Windows 7. The code I am using is:

            try
            {
                // Thread gives tooltip highlight time to disappear; can be made faster
                System.Threading.Thread.Sleep(1000);

                int screenWidth = Screen.GetBounds(new Point(0, 0)).Width;
                int screenHeight = Screen.GetBounds(new Point(0, 0)).Height;
                Bitmap bmpScreenShot = new Bitmap(screenWidth, screenHeight);
                Graphics g = Graphics.FromImage((Image)bmpScreenShot);
                Rectangle bounds = new Rectangle(Location, Size);
                g.CopyFromScreen(0, 0, 0, 0, bounds.Size);

                SaveFileDialog dialog = new SaveFileDialog();
                dialog.Filter = "JPEG Image|*.jpg| PNG image | *.png";
                dialog.Title = "Save As";
                dialog.ShowDialog();

                if (dialog.FileName != "")
                {
                    FileStream fstream = (FileStream)dialog.OpenFile();
                    switch (dialog.FilterIndex)
                    {
                        case 1:
                            bmpScreenShot.Save(fstream, ImageFormat.Jpeg);
                            break;
                        case 2:
                            bmpScreenShot.Save(fstream, ImageFormat.Png);
                            break;
                    }
                    fstream.Close();
                }
            }
            catch
            {
            }
            finally

            {
            }

Could somebody please tell me why this isn't working ... Thanks for your help ...