Wired connection is working but WiFI isn't

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http://askubuntu.com – I installed Ubuntu 12.04 on my laptop alongside Windows 7. My problem is, a wired internet connection works very well but I'm not able to use a wireless network which is in my home. Another information, I was able to use the same wireless network during the installation of the OS. I got disconnected in the middle and since then Im not able to use it. Im new to Linux so I request any of you guys to please help me with this issue. Thank you. (HowTos)