I need a software like Caffeine to simulate keypress periodically. Unfortunately with Caffeine I can't configure which key to press and not happy with its default.
This one reviews very well (4/5), and was lean when I installed it (only 36K) on a test comp. You don't say what OS, but it is also tested through Vista, so probably also runs on Windows 7. It is freeware.
http://eng.softq.org/small_utils.htm (Anti ScreenSaver).