Can your monitor display this

http://www.lagom.nl/lcd-test/black.php

Does your monitor show the first 3 squares on this LCD test?

Yes, it's usually an issue with contrast or brightness settings if you can't see test images properly. Change them. Unless the monitor is old or going bad, should have no issues with adjusting settings to proper ranges.

Neither LED backlight nor using a VGA cable should cause the image issue. If you have DVI on the video card, use that, it's a clearer and sharper image, especially at higher resolutoins.

Adjust both contrast and brightness, just one or the other may not do the trick. The first few squares should be a bit hard to make out, they just should not be black.