External LCD for laptop

I purchased a new mini-LCD display at www.lcdtft.com to connect to my laptop. It is the lcdm84vga under the “rack mount LCD monitors” link, first item, second row. I was assured by a Dell rep that this would work. It did not, but when I connected my desktop monitor to my laptop, it worked perfectly. I got zero response from the mini LCD.
System:
Dell E1505
Vista Home Premium
VGA connection
There is an s-video cable on the mini, but I was told attaching this to my laptop was unnecessary.
The mobile center interface on the laptop shows the mini is connected.
What’s up?