The screen on my HP Pavilion zt3000 laptop has changed and I don't why or how.
It seems bigger on the left and right sides, but not the top or bottom. It doesn't seem to be related to the screen resolution.
Any ideas what might be wrong?
Graphics card drivers usually provide a way to "move" the visible screen area around the monitor. You can normally get to your graphics card driver settings via a menu entry when right-clicking on the desktop, or via the control panel.
However, your laptop and its video card are pretty old, so you will have to rely on the HP drivers (updates are on their website), rather than the unified drivers offered directly from AMD/ATI and Nvidia. Its possible this setting for moving the visible area might not exist on your PC.
Try accessing your screen's OSD menu (via its physical buttons) and search for horizontal distortion. On my (HP) display, it's called "Custom Scaling".
On Dell :
Giving us your LCD model might help us guide you through this.