My monitor can't display anything from my CPU?

\How do you fix a monitor that doesnt display anything when computer is turned on?

• I left my computer on youtube for 20 minutes while i was eating breakfest and when i went upstairs, it was frozen. I decided to restart the computer. Once i restarted it, i tried turning it back on. The desktop monitor turned on but my screen monitor for some reason stayed black and the green light was flashing on it. I then checked all the wires for the monitor and my desktop. It was all fine. Then i took off all my wires for 1 hour and then turned it on again but same problem. Then i went in the computer and took out some of my ram and left 1. Then i tried again and it didn't work. The power supply is working i hear the windows sound and everything. I dont think its the monitor. Its workingg but just stays on black screen. and the green light flashes. Guys i cant see the bios, at all. All i can see is the black monitor screen as it would be when its turned off and its not the virtual black (black screen of death) .... its actually the black when ur screen monitor is off... but the led light beside the button for the screen is flashing green and that happens when the computer is off, but its not i turned the computer monitor on.... i need help

• Answer:

  Is the monitor plugged in? Does the monitor work when you plug it into another computer? Does the computer work when you plug it into another monitor?