So, you can get online with a wired connection? Dell uses a couple of different wireless modules so, which driver you need depends on which one your laptop has.
When you go to device manager, and click on network devices, does it show you have two? If so, and one of them is flagged, then you indeed need a driver for it.
If you turn the laptop off, unplug it and take out the battery, you can remove the small door which access' the wireless module. It should either say "Intel" or "Dell 1450 which is a broadcom chip.
Dell has a very handy utility for all the broadcom chips which you can download from their service site for your model.
Or, you may discover you don't have a wireless module, or you do and just need to configure the device so windows manages it.