My colleague also has some problem with his Dell Wireless Hardware it's not getting any signal from the Router even if the laptop is near, what we've done is;
Download the proper driver of your wireless adapter on your DELL Laptop get the model no. of your Dell then go to website of DELL itself and download the same Hardware Driver. Or if not, do not use the Wireless software of the DEll, use the windows wireless connection manager <--- a must!