Check your power options. Your system is likely going to sleep, not turning off. By default, computers are set to go to sleep after (i believe) 30 minutes.
Just to update. The computer was
entering "Sleep Mode".
I guess this is set to 30 minutes (by default) in Windows 7.
So I did the following to turn off "sleep mode"
1. Left-Click on Start - left side of the taskbar
2. typed in "Power" in the search area
3. selected "Power options"
4. selected "Choose shen to turn off the display" ( on the left side)
5. Selected "never" from the dropdown under "Put the computer to sleep"
6. Save Changes
Thanks again goes out to "The_Prophecy"