Turning off your monitor or laptop screen from within Windows isn't easy. MonitOff ($17, 30-day free trial) is an attempt at a simple solution: a tray icon that powers down your monitor when clicked. Unfortunately, it's so buggy that it's almost unusable.
On my Vista system, MonitOff does not save any changes I make to the preferences. This is especially problematic because I can't disable the "Hold" setting, which is also broken--it freezes my cursor for three long seconds every time I wake up my computer's screen after using MonitOff. It also makes it impossible to enable keyboard support, which would be a very nice feature.
To be fair, the main function of turning off the screen does work. But even if Monitoff did work perfectly, the price tag of $16.99 would still be outrageous for such a simple program. Look to the freeware MonitorES instead. It does everything that MonitOff promises and more.