The Clipboard is a temporary storage area used by Vista. Information (such as text, files, graphics, sound, or video) can be copied to the Clipboard from one program or location and pasted elsewhere. The Clipboard can only hold one piece of information at a time. Whenever something is copied to the Clipboard, it replaces whatever was there before automatically.

This trick can be handy if you just want to clear the Clipboard without having to copy something else to do so. This way you do not have potential sensitive information just sitting in the Clipboard.

Here's How To: Create A Desktop Shortcut To Clear The Clipboard In Windows 7 Or In Vista

If you have Visual Studio 2008 Express or any Visual Studio 2008 Edition, you can just use Clipboard.Clear() with VB,Clipboard.Clear(); with C#.

You can put these functions under the Form1_Load method and close the application using Application.Exit() for VB and Application.Exit(); for C#.

This will clear the clipboard and close your application immediately.

Here is an article which describes how to use windows clipboard using native Win32 functions.
Writing to Windows Clipboard