From the Samsung website faq help. If your computer doesn't recognize your LCD monitor, try these suggestions: If you used your old signal cable when you installed your Samsung monitor, replace it with the cable that came with the monitor. Make sure that the signal cable between your monitor and computer is connected securely and completely to the back of your monitor and to your video card. Note: If your signal cable is not connected correctly, your monitor will display the "Check Signal Cable" message. Check the video card in your computer and make sure it is fully and securely inserted. If you are using a DVI cable, press the Source button on your monitor and make sure that the source is set to Digital. If the Power Indicator LED on your monitor is blinking, your monitor may be in Power Saving mode. Try pressing any key on your keyboard to activate the monitor. If there is still no image, press the Source button on your monitor, and then press any key on your keyboard. If your are using DVI cable, and you disconnected the DVI cable when your PC was running, or booted your PC before you attached the DVI cable, shut down your computer, reconnect the DVI cable securely, and then reboot your computer. If the suggestions above do not resolve your problem, run a monitor self-test to check whether your monitor is functioning properly. To run the self test, follow these steps: Turn off both your computer and the monitor. Unplug the video cable from the back of the computer. Turn on the monitor. Depending on your monitor, one of the Check Signal Cable figures shown below appears. Note: While in the Self-Test mode, the monitor's LED power indicator remains green and the Check Signal Cable figure moves around on the screen. Test Results If the monitor does not light up when you perform the self test, most likely the monitor backlight has failed. If no Check Signal Cable figure appears, there is a problem with your monitor. If you see the second figure, and one of the colored squares shown above within it does not appear, there is a problem with your monitor. However, if you see one of the Check Signal Cable figures as they appear above, the problem your are having is probably with your video controller, video cables, video card, or computer system. Your monitor is functioning properly. If you did not see a Check Signal Cable figure, a colored square did not appear, or your computer still does not recognize your monitor, call Samsung Customer Service at 1-800-SAMSUNG (1-800-726-7864) for additional help. Have the model number and serial number of your monitor on hand when you call.