1. Adjust the brightness of the LCD panel. Check your laptop's Manual for steps on how to increase the brightness.
2. Tilt the LCD panel before and after Windows screen appears and see if this affects the brightness . If it is, this indicates a possible loose connection between the LCD cable and motherboard. Removing and reattaching the LCD panel cable may resolve this issue. Before doing this, please take anti-static precautions. Please check your notebook service manual for accurate steps.
3. If possible, try attaching an external monitor to your notebook and toggle the display onto the external monitor. If the video display on the external monitor is bright and vibrant, this rules out any problems with the graphics chipset.
4. If your laptop manufacturer has provided the diagnostics, please check the LCD brightness by running the tests.