After installing the Operating System you must install the drivers in the order mentioned in this link. "Dell QuickSet Application" controls the `Fn' key behavior. If you have installed all the drivers in the correct order then you can download the "Dell QuickSet Application" from here. You can check the devices such as Wireless Card in the Device Manager and then download the drivers from here.
Please revert for clarification.
To know more about Dell's products, services and drivers & downloads, please go to http://dell.to/YBlak6