Problems on startup

When I turn on my PC, all I get is a blank screen, and lots of beeping noises from the tower, although after removing the CD-ROM from the CD-ROM drive there is less beeping, but still the blank screen.
There seems to be a problem with the monitor, because it keeps turning on, stays blank for a while, and then turns off again. I've tried unplugging the monitor, and it comes up No Signal Recieved on the monitor as you'd expect, and a little bleeping from the tower.
I can't tell if the computer is working 'properly' as I kept getting blue error screens upon startup, so there's no sound I can listen out for to check if it is starting up properly, but just not being shown on the monitor!

Anyone got any ideas of what might be wrong, or what to do?!?
Any help much appreciated!

 

Try to diagnose from those beeps - http://www.computerhope.com/beep.htm

 

Thanks for the help. I've looked it up, and it says this:
"1 long, 2 short Indicates a video error has occurred and the BIOS cannot initialize the video screen to display any additional information"
Does this basically mean my monitor isn't working any more? Any solution to this other than buying a new monitor? Thanks again.

 

Actually, just thought the monitor can't be broken, as it is displaying the no signal recieved message just fine when I unplug it completely. I've just had a look at the monitor cable, and there appears to be a pin missing (pin 7 according to the diagram on the first link I was given). Is this normally missing on some cables? It would have to have broken off inside the computer, as it only suddenly stopped working, but I can't see it inside the monitor port on my tower...