If you have Windows 7 on your desktop computer then it's a little difficult to find how to disable your computer from hibernating or going to sleep after a period of time.
The steps are quite simply actually, here they are:
1. Open Control Panel
2. Change "View by" from Category to Small icons
3. Locate and click on Power Options
4. By default Balanced radio button is selected - so click Change plan settings on the right
5. Change settings to your desired selection and press Save changes button.
That's all now you don't have to worry about your desktop computer going to sleep or hibernating while you're away from the keyboard.