PC Will Not Boot/Start

Hi There,

While using my PC my monitor screen all of a sudden went blank "Attention no signal, please check input connection or signal", after checking the connections and the monitor, I then tried to restart my computer, I simply powered off and on again, however the screen remained blank, and I was sure I did not hear it boot up correctly, so after several attempts I am convinced it is not booting correctly.

I then tried my OS CD, however I cannot get that to boot the PC with the same message on my monitor screen.

I am really at a lose if my OS CD cannot boot.
I am not aware of any changes recently and there has no major changes to my PC.

Any help appreciated, thank you.

Windows Vista OS