Caffeine

Operating systems are usually set to go to sleep mode automatically if no user activity is detected, so the computer would use less power. Despite its usefulness, this feature can be annoying sometimes, especially if you don't have the administrative privileges to disable it. Fortunately, you can use Caffeine to prevent the computer from going to sleep. This simple application simulates a key press every 59 seconds, as if you were using it.

Caffeine is absolutely free and it works on all modern Windows platforms. It comes in a small package and it doesn't need to be installed. Also, there are no special requirements you have to meet and you won't notice any effects on your computer's performance.

Extracting Caffeine's executable from its archive and running the application is all you have to do. The application doesn't come with a user interface, but it doesn't even need one. You can activate it and deactivate it at any time by simply double clicking its system tray icon.

As long as Caffeine is active, it will prevent your computer from going to sleep, as previously mentioned. What's more, you can right click its system tray icon to reveal options for making the application active or inactive for a limited period of time. You can choose between one hour and a whole day.

Thanks to Caffeine's straightforward functionality, a single click is all it takes to prevent a computer from switching to sleep mode.