Author: Jonas Bilinkevicius 

When I make a change to the registry, some applications do not seem to acknowledge 
the changes until they are restarted. How can I get the applications to respond to 
the changes? 

Answer:

Broadcast a WM_WININICHANGE message to the system, sending a null terminated string 
detailing the registry section that changed. Most well written applications should 
respond to the WM_WININICHANGE message. 

Example: 

1   procedure TForm1.Button1Click(Sender: TObject);
2   begin
3     SendMessage(HWND_BROADCAST,
4       WM_WININICHANGE,
5       0,
6       LongInt(PChar('RegistrySection')));
7   end;