C#

<br />
  public class Joshua : Form {<br />
    [STAThread]<br />
    public static void Main() {<br />
      Application.Run(new Joshua());<br />
    }<br />
<br />
    public Joshua() {<br />
       this.ClientSize = new Size(520, 310);<br />
       this.Name = "Form1";<br />
       this.ShowInTaskbar = false;<br />
       this.SizeGripStyle = System.Windows.Forms.SizeGripStyle.Hide;<br />
       this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;<br />
       this.TopMost = true;<br />
       this.TransparencyKey = System.Drawing.SystemColors.Control;<br />
       this.Opacity = .8;<br />
    }<br />
<br />
    protected override void OnKeyDown(KeyEventArgs kea) {<br />
      if(kea.KeyCode == Keys.ControlKey) {<br />
        this.TransparencyKey = System.Drawing.Color.Empty;<br />
      }<br />
    }<br />
<br />
    protected override void OnKeyUp(KeyEventArgs kea) {<br />
      if(kea.KeyCode == Keys.ControlKey) {<br />
        this.TransparencyKey = System.Drawing.SystemColors.Control;<br />
      }<br />
    }<br />
  }<br />
<br />

public static uint UpdateCRC( uint CRC, byte[] buffer )
{
   for ( int i = 0; i < buffer.Length; ++i )
   {
      CRC = 
         ( CRC >> 8 ) & 0xFFFFFF ^
         CRCTABLE[ (byte)( CRC & 0xFF ) ^ buffer[i] ];
   }
   
   return CRC;
}