Did you try to you may reseat the wireless card, you can follow this link to reseat the wireless card, http://dell.to/cn6CxY.
This is the first thing that you have to do!!!!
Let me know if it work for you.
I see that the wirless card is getting detected in the device device manager, but the driver is not installed correctly. If you have the drivers cd, go ahead and install the driver for the Intel 3945 card. You can also download the driver off our support site, by following this link http://dell.to/cdtNxV, please make sure you select the correct operating system before you install. Let me know if that worked.