Hi!
Can you give me the exact model of the laptop? And the operating system details as well?
First thing you can do is to press the Fn( Function) + F7 key. That is how I activate the second monitor on my laptop. That's the reason why I need the exact model also to give you the exact keys to press. Anyway, if you have tried that and still nothing works, you can check the monitor settings under the Display control panel. Just right click on your Desktop, hit Properties and then Settings. This is for Windows XP by the way. You should see two boxes with numbers 1 and 2. The first one is your default monitor. The second one is for any other video output which goes out thru the VGA cable. If the computer detects that there is a monitor hooked up on the port for the second monitor, the window 2 should not be greyed out.
By the way, you can also play with the screens resolution. If it is set too high, try to lower the resolution.
If you can provide me with the additional details I need, maybe we can work on this faster.