Instructions:
Click the Start button and point to Control Panel. When in Control Panel, double-click Administrative Tools. Look for Services and double-click it. When in the Services window, look for Wireless Zero Certificate, right-click it, and select Properties. When in Properties, click to select Automatic from the drop-down menu beside Startup type. If it is already set to Automatic, don't worry and simply reselect it. When done, click the Apply button and then OK to exit the Properties window.
Navigate to Control Panel and double-click Network Connection or Network & Sharing Center (whichever you see there). Look for your wireless network connection, right-click it and select Enable. Again, right-click the wireless connection and point to Properties. Highlight the Wireless Networks tab and make sure that the box beside Use Windows to configure my wireless network settings is checked. If it is not, do the needful. Click the OK button to exit Properties. Close all the windows and restart your computer. Reconnect to the wireless network and check whether it works or not. Skip to next step if the problem lingers.
Click the Start button and point to Run. When in the Run dialog box, type 'cmd' and click the OK button. It will open up the Command Prompt window. Type 'ipconfig /release' (without quotes and as is) and hit the Enter key on the keyboard. In case you see an 'access denied' error message, exit the window. Log off your computer and log back in as an administrator. Open Command Prompt and run the command again. When done, type 'ipconfig /renew' and hit the Enter key. This will renew the IP address of your wireless connection. When done, type 'ipconfig /flushdns' and hit Enter. Exit the window and restart your computer. When done, reconnect to your wireless connection and check back. If the problem persists, skip to next step.
Open Command Prompt again. Type 'netsh winsock reset' and hit Enter. You may also type 'netsh winsock reset catalog' instead of the previous command. When done, you will see a message like 'successfully reset the Winsock catalog, restart your computer'. Restart your computer. When done, reconnect to your wireless network and check back. If the problem lingers, reopen Command Prompt and type 'netsh int ip reset reset.log'. Hit the Enter key to execute the command. When prompted, reboot your computer.
If you get a 'radio disabled' error message after replacing the power jack in your Dell laptop, try this method. Click Start and point to Run. Type 'regedit' in the Run window and hit Enter. When in Windows Registry Editor, branch out HKEY_LOCAL_MACHINE by clicking the + button next to it. Navigate to Software> Microsoft> Windows> CurrentVersion> Run. Under Run, check if you see any third-party LAN MANAGER entry. If there is any, delete it. Now navigate to HKEY_CURRENT_USER> Software> Microsoft> Windows> CurrentVersion> Run. Under Run, check for LAN MANAGER entries and remove if there is any.
Other than these methods, make sure that you are using the right channel number for your wireless connection. Open your web browser and visit the Dell website. Navigate to Drivers and Downloads section and look for the driver file of your Dell laptop model. Download the driver file and save it to your computer when prompted. Exit the browser window and go to Downloads folder or to the place where you saved the file. Open and execute it. If it is a zipped file, unzip its contents to another folder and save it. Thereafter, open and execute the file. Follow the on-screen prompts and update drivers of your Dell laptop. Reboot your computer afterwards. Check back, if the wireless connection works or not.