To find running instance

hDeskWnd = GetDesktopWindow, gives the desktop window. All the the other windows are its children. Using the desktop window pointer,

while(null != (hChildWnd = (GetWindow(hDeskWnd ,5)))

{

GetWindowTextA(hChildWnd,strBuffer,bufLen);

Now compare the strBuffer to your window title which appears on the top left corner of your application, if it matches, your application is running

}

GetWindow - gives all the children of a given window, for desktop all the running application windows !!!

If you want to do it from Installation, check the option to call a dll function in the installation tool, the functions are in system32\user32.dll.

Good luck