Q: API FindWindow
"One way you can try to detect if an application is running is to
Call FindWindow passing its Window Class. You can use the application
from Q112649 to find what the class name of the application.
As long as a window with that class exists on the system FindWindow
should be able to locate it. If FindWindow return 0, then the window
does not exist."
It seems logic... on the site you find a executable TaskList (it's 
also in source code on the site). This will do what MS tells you.. it 
will find all open windows (searching for the proper caption).
So if you are looking for solitaire you start the program with the 
parameter 'Solitaire' (which is the window-caption). If it's found 
(see the source code) you can do your thing... if it's not found you 
know that it isn't open.