hi! 966 is compatible with Vista machine.. what type of wireless adapter you're using? is it 3300 or Internal Network Adapter?

It must be the internal adapter, though I am not certain.  I bought a new laptop from Dell along with the printer.

To print wirelessly you must have the printer attached to a wireless router and make it part of your network. Did you purchase the network card for this printer so you can attach it to a wireless router? Do you have a wireless router? Your computer may have a wi-fi (802.11x) adapter but that is so the system can connect to a wireless router but then your printer needs to be connected to that router also. 

 

In order to confirm if the network card is in your printer please go to this link for the User's Guide. Once the User's Guide is open click on the Search tab and search for NETWORK. A list will come up and you will see "Installing the Dell Wireless/Ethernet Card." Click on this and on the right scroll down and there'll be a picture showing how to install. If this card is already installed you'll just need to configure it correctly to your wireless network.