how do i prevent screen-savers and sleeps during my program execution?

That's not a bad idea, any decent media player does it... Look for SystemParametersInfo(SPI_SETSCREENSAVEACTIVE ...) function in Win32 api, it should do the trick.

Don't mess with the screensaver settings, use SetThreadExecutionState. This is the API for informing windows on the fact that your application is active:

Enables an application to inform the system that it is in use, thereby preventing the system from entering sleep or turning off the display while the application is running.

, and

Multimedia applications, such as video players and presentation applications, must use ES_DISPLAY_REQUIRED when they display video for long periods of time without user input