Put a menu bar item to temporarily disable sleep and screen savers.
Caffeine for Mac is a great utility for preventing the computer from starting its screensaver, going to sleep, or automatically dimming its screen after a period of inactivity. It's like serving your computer a cup of coffee, so that it remains awake, just like the user does while watching a movie or reading a document. Caffeine is very simple to activate: just click on the coffee icon on the Menu bar to enable it and then click again to disable it.
Force your Mac to stay awake or set up a scheduled wake time.
free full system DL, not update, if you don't have System 7.5.x in any form
Makes closing of your MacBook lid possible without going to a sleep mode.