Reason Analysis:
This is because the computer installed system is a key ghost or driver wizard updated graphics driver caused by the graphics driver exception, so that the brightness of the computer can not be normal debugging. So the previous video card driver uninstall, restart the computer, and then install Lenovo's official website graphics driver can.
Solution:
1. Click Start---Control Panel---program and function (or "program" under "Uninstall program"), find the name with Nvidia name software, right-click, select Uninstall. For example: NVIDIA graphics driver, nvidia Physx,nvidia update, and so on, click the right button, choose Uninstall;
2. Then find the name of the Intel HD Graphics (or Chinese "Intel (R) Core graphics driver") software, click the right button to choose Uninstall.
Due to a system installed by one-click Ghost Installation, there may not be a graphics driver in the list of programs, then uninstall in Device Manager. Exit to the desktop, then right-click the computer's icon, select Manage, then click Device Manager, and in Device Manager, uninstall the program shown in the diagram:
Uninstall this here, first uninstall the computer's stand-alone video card, is GT740 this, and then uninstall the above Intel Start program. Reboot the computer after the uninstall is complete, and then install the graphics driver.