Monitor alone not getting turned on!

Hi DJ,
I have come across with a problem which i could not sort it out.

When i switch on the power supply,fan is on,cd rom is opening and the hardware light is also on bt my monitor is always in off mode.I couldnt hear any beeps at the start up of the PC which i waz able to hear b4 facing the problem.Am not getting signals to monitor.Tried al the methods tat u mentioned but no improvements.

Monitor waz working fine bt then suddenly it stopped its displaying agenda.Can u suggest me wat shld i do and wat cld hav caused the problem??