Desktop not working, need help!

[nosignal1]

Okay, I have an emachines desktop which i got about 6 months ago. Today, when i went to turn it on, the green light came on like normal, then i turned the monitor on, but it said that there was no signal coming into the monitor.
When I turned the computer on, I heard the hard drive start up and the fan on the power supply is working.
I have no idea what's wrong. Can anyone help me?

 

[kmote]

Have you checked your VGA cable is plugged in tightly?

 

[-RockMan-]

Also did your computer happen to do any post beeps if you don't get any kind of beeps you will need to start testing your hardware.

We know your hdd is functioning because you heard it spin up, you should have noticed your cd-dvd drive doing it's normal post up with the system.

Three things I check now is: ram first, second try cpu by removing all ram and see what happens.
Last if your mobo does not respond to anything it maybe it fault, but we'll find out that later when you post back.