Can connect to LAN but not wifi

Hi,

I can connect to LAN but not WiFi on my Sony VAIO laptop. It connects to WiFi when I go close to the router. But it disconnects if I move five feet far. While all other services next to me are connected. Please help

Error message : please make sure that the network is in range and the property of router and settings are the same.

OS : windows 7

My touchpad wasn't working. And I had a local vendor repair it. From that day on, this WiFi issue has started
 
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