LCD is way to bright to see. No contrast. Works

To help you change the brightness and contrast settings from the LCD monitor, please follow the instructions mentioned below,
The control buttons are located at front panel of the monitor. The Brightness Button is used to select the Brightness/Contrast adjust functions. Press to switch functions or adjust settings.
To decrease the brightness or contrast press (-) button & to increase (+) as per your adjustment.

GuruAid.com

Try plugging in another working monitor into the monitor output - if results are the same then the problem lies with your video circuits in your all in one. Hopefully it is under warranty - if not you are screwed because those all in one units have nothing but proprietary parts and are very costly to replace/service. If the external monitor works fine then the problem lies with the display or screen of your all in one.

It's time to RESPONSIBLY RECYCLE any 17-inch CRT monitor, and buy a LCD monitor;
used LCD monitors can be purchased for under $50.

It would cost you over $50 to take the CRT to a TV/Video repair shop, for trouble-shooting and repair.

From p.29 of the manual

"Brightness, Contrast, Sharpness, Color, and Tint are only available for adjustments
if you select User in Picture Mode.
Press / on the remote control or VOL+/ VOL- on the control panel to adjust these settings."

I have downloaded the manual from Hyundai website en_man_monitor_lseries_l52s.zip

The up/down button on your flat panel is stuck. Please contact Hannstar Technical Support to have the monitor replaced if its still within warranty.

if you go into the screens menu, there will be a button for contrast and brightness.  When you have the one you want selected, press munu again and that will bring up the dialog to change the percentages.

The monitor and laptop are not compatible or the cable is not properly connected.

If the backlight lights up for a second it's probably fine - It lay odds on the display inverter in the screen. Actually finding parts for anything made by gateway may be difficult, however. They do not sell spare parts. Considering the size of the LCD i bet it would almost exceed the replacement cost of the screen to repair it

It looks like your UP button contact is demaged.
SOLUTION is to insert a piece from your business card mostly above the button to adjust it down or up. It works fine.