Fn + F7 (on most Vaios) is the right solution for what you want to do.
It toggles monitor options between "laptop-screen-only," "external-monitor-only" or both screens. On the "both screens" setting, you will still see a clone of the same screen on the laptop and the desktop.
You might have something else going on besides the bad screen.
THANKS FOR THE INFO! I am pretty sure my video card is toast. Have already purchased a new laptop as the notebook has seen its better days. I want to transfer my data from the notebook to my new laptop. Is there an easier way to do a data transfer without removing the old hard drive? Keep in mind the is no screen on the notebook. Also I am running XP on old notebook and Windows 7 on the new laptop.