I don't think this problem is related to your laptop. This happens because of windows setting. If you have Windows Vista installed then it has option 'sleep'. The option might be set if system idle for such a time then go to sleep automatically. They you have to turn it on again but you still find all the data on which you were been working. Check the system properties and correct it.
Check the power settings and there is a display option. Also, there is a function control that may be helpful. Usually it is the F7 key. By pressing the FN key and then the F7 key at the same time it changes the display from the VGA port to the screen to both.