On my Lenovo Laptop, occasionally, the display goes all the way down to the lowest contrast. And then it comes all the way back. Is there any way that I can eliminate this forever?
By "contrast" do you mean brightness?
The power managment software does automatically dim the screen after a period of inactivity. You can normally avoid this by choosing the correct power profile for your current task. For example, if you're watching a film, you should use the "Video Playback" profile.
Windows 7 also have a similar feature built-in (as a system service), but it should be managed in power profiles as well.