Dell st2210 backlight - Dell ST2210 21" Monitor

press the button 1 and button 4 together for 2-3 seconds and it should work,

If your LCD TV or monitor has stopped working, or is displaying one of the following symptoms, then it's a candidate for some new capacitors
- Flickering screen
- Screen image disappears after several seconds
- Dim screen
- Slow start
- Power LED on, but no picture
- Unusual colors and/or lines
The primary cause of LCD TV and monitor failure is caused by faulty capacitors. You can examine the capacitors in your LCD TV or monitor and actually see if they are bad.
If they appear bulged on top, then they need to be replaced.
New capacitors will solve a host of problems in LCD monitors and TV's and will extend the life of your monitor or TV by several years.
Check the cables, connectors and connections.
Take it to a repair shop.

You need to test the DVI port and use the DVI-VGA adapter if your computer does not have a DVI port.

please check proper powersupply & when power is ok then open the monitor & check fuse ,main filter capacitor& bridge diode.

I would like you to run a self test on the Monitor to make sure that the monitor is working fine.
Self test on Dell ST2210

Not really, this looks like a pressure mark which has damaged the screen surface. Easily done by pressing the screen with a finger or pencil / pen.

You must check Monitor Cable with your PC -> plug-in to VGA Output

Have you tried a spare monitor to make certain it is not the computer? because this will prove if the monitor is a fault or the computer. By your description the problem is in your computer.

http://www.nodevice.com/driver/A9250/get37525.html

Connect the monitor to some different computer, e.g., a laptop, to verify that the monitor is working.
If not, take it back to DELL/STAPLES, and get them to check it out, or to exercise the "warranty" to get it repaired/replaced.