cant scan for wireless network

hi, i purchased my dell 5423 about a year ago and i have always been able to connect to wifi, but a few days ago my computer stopped scanning for wireless networks, i have tried troubleshooting but unable to find a solution. i have go to 'turn wireless device on or off' under network - devices, it says "we couldnt find a wireless device on this pc", i have tried redownloading the driver from dell support website but installation is always unsucessful. Anyone can help with this.