[ubuntu] Video device not detected in Ubuntu 12.04

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http://ubuntuforums.org – Hi guys, I have a Dell notebook with GeForce GT 630M 128-bit 1GB with Nvidia Optimus. Actually, I needed to install Nvidia drivers so I could use Nvidia CUDA technology. When I reboot my Ubuntu 12.04, something happens and a message is displayed saying that the video device couldn't be detected, and all I have is the text mode, the GUI mode is unavailable. I already tried to reinstall Nvidia drivers, but that doesn't work either. . I had to reinstall Windows. :( . Does anyone here know what should I do? . Thanks in advance, (Hardware)