Author: Tomas Rutkauskas 

After changing the registry...

Answer:

If you change a registry entry that is being used by another application, it's a 
good idea to let that application know what you did so that it's able to update / 
refresh itself.

Just notify all running applications by sending a message to all the windows about 
your action as follows: 

SendMessage(HWND_BROADCAST, WM_WININICHANGE, 0, LongInt(PChar('RegistrySection')));

"RegistrySection" is of course the registry section which you changed. 

If you're using Windows 95, you may have to use "WM_SETTINGCHANGE" message instead 
of "WM_WININICHANGE."

Also, it's possible to use Win32 API function "SystemParametersInfo()" to send out more specific notices about registry and/or system parameter changes you make.