Error:There is no signal from your computer

Hello,
Please help me, As soon as I switch on my computer the monitor enters into the power save mode and then stops displaying anything on it and there is the yellow light glowing, if I press any button on the monitor the the error message displayed is:"there is no signal from your computer, press any key on the key board or the mouse to wake up and to connect to another power supply press the button on the monitor" my cpu is in the good condition and all the fans are spinning and the hard drive is also fine so please help me in this to solve the issue
Thank you,
Regards,
Manoj