Lenovo ThinkPad T420 User Manual page 237

1. Connect the external monitor to another computer to make sure it works.
2. Reconnect the external monitor to your computer.
3. Refer to the manual shipped with the external monitor to check the resolutions and refresh rates that
are supported.
– If the external monitor supports the same resolution as the computer display or a higher resolution,
view output on the external monitor or on both the external monitor and the computer display.
– If the external monitor supports a lower resolution than the computer display, view output on the
external monitor only. (If you view output on the both the computer display and the external
monitor, the external monitor screen will be blank or distorted.)
• Problem: You cannot set a higher resolution than the present one on your external monitor.
Solution:
– Make sure that monitor information is correct. Do the following:
For Windows 7:
1. Right-click on the desktop, and click Screen resolution.
Note: If your computer cannot detect the external monitor, click the Detect button.
2. Click the icon for the desired monitor (the Monitor-2 icon is for the external monitor).
3. Click Advanced Settings.
4. Click the Adapter tab.
5. Make sure that the correct device driver name is shown in the adapter information window.
Note: The device driver name depends on the video chip that has been installed on your computer.
6. Click OK.
If the information is incorrect, reinstall the device driver. See below for more information.
For Windows Vista:
1. Right-click on the desktop and click Personalize.
2. Click Display Settings.
3. Click the Advanced Settings button.
4. Click the Adapter tab.
5. Make sure that the correct device driver name is shown in the adapter information window.
Note: The device driver name depends on the video chip that has been installed on your computer.
6. Click OK.
If the information is incorrect, reinstall the device driver. See below for more information.
For Windows XP:
1. Right-click on the desktop, and click Properties to open the Display Properties window.
2. Click the Settings tab.
3. Click Advanced.
4. Click the Adapter tab.
5. Make sure that the correct device driver name is shown in the adapter information window.
Note: The device driver name depends on the video chip that has been installed on your computer.
6. Click OK.
If the information is incorrect, reinstall the device driver. See below for more information.
.
Chapter 10 Troubleshooting computer problems
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