Amphetamine will help prevent sleep modes and screensavers, and also your system from shutting down/restarting.

Fully portable, and intended for PC tech usage, Amphetamine includes the ability to prevent three things, (all are individually optional): Screensaver, Sleep Mode, and System Shutdown/Restart. While there are other similar apps designed to prevent screensaver and sleep modes, there aren't many that prevent Windows from shutting down as well. FoolishIT has additionally added more extended functionality that you won’t find in the others.

Optional/extended functionality for performing custom actions when a shutdown/restart is initiated and prevented by Amphetamine include:

Ensure preconfigured services are started.
Ensure preconfigured programs are running.
Run a program/script.
Email you (the administrator) notifying you of the prevention.