Helping people with computers... one answer at a time.
No Signal is a message that's not from your computer but from your display device, indicating that it has nothing to display. I'll review possible causes.
I am using Window XP and just started to get a No Signal message when trying to start up. When I push the Panic button on the tower, it starts. Everything works normally after the start. What's going on?
This message actually confuses many people, so you're not alone.
The issue here is that the message is not coming from your computer.
In fact, that's the problem.
Confusing, I know. I'll explain.
Your desktop PC is typically connected to an external display device that's variously referred to as the monitor, screen, or display. The video card inside of your PC turns the bits and bytes that represent the image that you see on your screen into a signal that travels along the cable connecting your computer to the display.
And therein lies the clue...
The No Signal message does not come from your computer - it's generated by the monitor itself. All No Signal means is that the monitor is not receiving a video signal from the computer.
That's a pretty simple explanation. In fact, from the monitor's point of view, it's a pretty simple situation: it's expecting a signal, telling it what to display, and it's not getting it.
It's easy to overlook some of the possible causes:
The monitor is on, but the computer is not.
The cable connecting the computer to the monitor has become disconnected.
The cable connecting the computer to the monitor is faulty.
The monitor has multiple inputs and the wrong one is selected. (This is common if your monitor is actually a TV of some sort.)
The computer has multiple screen outputs and the one that the monitor is connected to is not enabled. (This is very common when trying to get an external monitor to work with a laptop.)
The computer has crashed in such a way that it's not trying to display anything.
The computer is broken in such a way that it cannot boot. (Lights and fans running doesn't mean much in this case.)
And, of course, the monitor itself could be broken.
As you can see, there are many possible causes for a simple error message.
When faced with this situation (and I have been!), I check to make sure that everything is on (it's so embarrassing when it's not ) and that the cable is properly connected. If that doesn't resolve it, then I move on to trying another cable or monitor and finally attempting to diagnose whether the PC is working at all.
Monitors and PC displays have become sophisticated devices in their own right and may often display messages of their own as a result. In the case of no monitor signal, it may be the only thing on the screen.
Other monitor-generated messages will often appear "on top of" whatever else your computer is displaying. There's typically nothing that you can do to your computer to get rid of those messages because they're not from the computer, they're from the monitor. Understanding what they look like and what steps need to be taken means becoming familiar with your monitor's options and controls - something completely separate from the computer itself.