Go to Control Panel\All Control Panel Items\Power Options and change the Plan Settings.

In "Change advanced power settings" look for Sleep and Display.

got this off the net hope it helps but beware it involves editing the registry.

If your computer is having issues with Windows 10, or Windows 8, going into sleep mode on it's own, this is the answer for you, I have currently had the same issue, Here is a tutorial upon how to fix it.

1. Click on the windows icon
2. Type regedit
3. Right-click on regedit icon, click Run as administrator
4. Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Power\PowerSettings\238C9FA8-0AAD-41ED-83F4-97BE242C8F20\7bc4a2f9-d8fc-4469-b07b-33eb785aaca0
5. Double click on Attributes
6. Enter number 2.
7. Go to Advanced power settings (click on Windows button, write power options, click on Power Options, in the selected plan click on the Change plan settings, click on the Change advanced power settings).
8. Click on the Change settings that are currently unavailable
9. Click Sleep, then System unattended sleep timeout, then change these settings from 2 Minutes to 20 for example.