Computer's Monitor No Signal Detected!?

hi, i am having a problem with my computer.. when i turn it on the sound and everything come sout of the computer like normal excep t it doesent beep when i turn it on, and the screen stay's blank and just say's no signal detected, and thats it nothing els happens.. i have tryed disconnecting cables, and reconnecting them.. i trying the pc on a different power point, i have tryed new cables, i have tryed a different monitor and nothing isnt still working ? any other idea's on what i can do.