UPDATE I have this working on a Dell XPS M1710 as well. This uses an Intel 3945ABG wireless card. Perform the same steps below and NS should work.

I have figured out how to get Vista and Netstumbler to work on the Dell Inspiron E1705 laptop.
First, go to Dell.com and download the XP driver for the wireless card you have installed on your laptop (typically Broadcom)
Next, run the downloaded executable but do not go through the installation process, just extract the files.
Next, go to your Device Manager in Vista and right click on the Broadcom wireless card.
Click on Update drivers.
Point Vista to the location where you extracted the Dell wireless drivers
Follow the appropriate "Next" buttons
Download and install Netstumbler 4.0 and have fun. It should work properly.

Still can't get NS to work?

Open a command prompt, type netsh and press enter

Next type:

wlan show networks mode=bssid


STILL cant get it to work for you? Download this C# application that will work. Its a Netstumbler clone that works with any wireless card. Vista compatible too :)

NetStumbler Replacement for Vista