Computer Not Booting Up - Please Help

My compter was working fine yesterday. Today when I went to start it up I got this blinking message on my monitor "Self Test- Check your PC and Signal Cable - Monitor is working" I checked all the cables to make sure everything was plugged in right. The computer turns on and I can hear the fan and see a light on it, but it does not try to boot up or make any noises other than the fan. Also I noticed that the cd and dvd drives will not open.

I need this computer for school in a few weeks. Can somebody please help me?