nothing in render window

Just installed the latest version of blender on a Vista laptop and when I render, the screen is black. Ive got the camera and lamps set up properly but doesnt want to show anything. It stays black even though I set the render background to blue. I even set ambient occlusion but It aint rendering…is this a video card problem?

Did it work before your latest installation?
Since I have my cameras and lights on their own layers I have been bit by not having them selected. Another thing that bites me is making sure that the mouse cursor is in the correct window (split screens and not all layers are used in most of them to avoid clutter).

Its the first time on this machine.
Its the default view with one view port only and only one layer