You can make the computer not go into sleep mode, using the section "power supply", which is "control Panel". Depending on what system you have, and which has a "control Panel", click once on the desired icon at the bottom of the folder or first go to "System and security".
Note the parameter list in the left window and select "setting sleep mode" (it may be named differently, depending on the type of computer and operating system version). In the opened window, activate the item "Never" to have the computer not go into sleep mode.
Select more power options. If you have a laptop, on the main page you can choose a balanced power mode and economy mode or high performance. The last of them automatically disables sleep mode and configures the laptop is only from the mains. In the left part of your screen and select "configure display off". Here you can disable dimming of the screen when the system is idle. Also there is an item "Action when closing the lid". In this section you can make the laptop not go into sleep mode when the user closes the cover (by default, the device always goes to sleep).
Configure the settings for the screen saver that appears on the screen if the computer is not used for a while. From the comfort of section of the power settings, click "Personalize" in the bottom left corner. Next, select the "screen Saver". Install a suitable period of time, through which will appear the screen saver or turn it off altogether.
Do not turn off the sleep mode unless it is absolutely necessary. It saves energy and protects the computer from overheating. In addition, most applications have their own settings, which you can prevent the computer goes into the sleep state during operation of the program.