Hi
No. It is not possible to find this out as it is OS dependent. If you want to serve only Windows users with your web pages, then you might be severely limited, since many people use other OS to access web pages.
In the case of an intranet where all use the same OS and IE, you might have to write a screen saver that communicates with your web page using Active X controls and then make that screen saver default.
Your question is certainly very interesting and I would be glad to find outif any one has a better answer.
Regards