This is an interesting issue of Windows 7.
Some customers reported that in the Power Options they have chosen 'Never' for 'Turn off the display'. However it keeps resetting itself to 20 minutes.
After further investigation, it was proved to be a compatibilty issue of HD Tunes Pro. That software is for hard drives testing and each time any test starts it resets power options.
It's not just the pro, I have the free HD Tune and it does the same thing.