When you say wireless card? Card slot, USB Adapter or On-board Wireless? Go into the BIOS and make sure on-board wireless is enabled. If you have installed the drivers for the miniPCI wireless then it's either not working or there is and issue on the system. Go to DELL and grab the correct driver for that wireless you have. If not then get a USB dongle wireless 802.11(b,g,n) and use that instead.