This function empties the clipboard and frees handles to data in the clipboard.
BOOL EmptyClipboard( )
Returns TRUE for success.
The function then assigns ownership of the clipboard to the window that currently has the clipboard open.
Before calling EmptyClipboard, an application must open the clipboard by using the OpenClipboard function.
If the application specifies a NULL window handle when opening the clipboard, EmptyClipboard succeeds but sets the clipboard owner to NULL.
OpenClipboard, SetClipboardData, CloseClipboard