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?
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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.
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PCs and display devices
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...
No signal
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 it.
Possible causes
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:
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The monitor is on, but the computer is not.
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The cable connecting the computer to the monitor has become disconnected.
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The cable connecting the computer to the monitor is faulty.
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The monitor has multiple inputs and the wrong one is selected. (This is common if your monitor is actually a TV of some sort.)
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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.)
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The computer has crashed in such a way that it's not trying to display anything.
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The computer is broken in such a way that it cannot boot. (Lights and fans running doesn't mean much in this case.)
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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.
Monitor Messages
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.
Article C4824 - May 19, 2011 « »
Leo A. Notenboom has been playing with computers since he
was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed.
After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers
to common computer and technical questions. More about Leo.
May 27, 2011 12:24 PM
I had this problem when I had to buy a new monitor. I kept thinking it was because the new monitor was bad and after 3 upgraded monitors later it turned out I really did need a new video card. It's very interesting to see all the different reasons why this might happen. Thanks for all your help, Leo and all responders!
May 31, 2011 11:14 AM
Had this problem for weeks.
My video card had an outdated revision.
Updated it and all problems are gone.
Video card:
NVIDIA GeForce FX 5200
Windows XP
May 31, 2011 7:43 PM
My monitor has given a no signal notice since I bought it. The monitor came with the package and has a built in speaker. They sounded like an old transistor radio (yes I am that old). So disabled the speakers in the monitor and attached my Bose speakers to the computer and I have great sound. It just keeps giving me the same signal.
December 9, 2011 5:37 PM
I use Windows XP Pro on a desktop. A few weeks ago after getting a Blue Screen of Death, I have the same problem and it's driving me crazy! I've checked just about everything I can check, including running several scans of various types and many of the suggestions in this article, including replacing the cable with a brand new one, but the only way I can get my monitor to display anything is to press F8 when booting up and hope I can select "Last known good configuration" before that menu vanishes and the screen goes black again. I have to try several times before the menu stays visible for long enough to do so. Once it's in Windows it's fine, I have no problems at all so if I'm going to be afk for a few hours or so I leave it on rather than go through all that hassle again. Unfortunately, I'm not a hardware expert so I'm reluctant to take the PC apart and I wouldn't know what to look for anyway.
May 18, 2012 7:40 AM
Hello
I get the "no signal" on my screen only after gaming.
I get no display what so ever so I am forced to use the reset button
so my problem is
computer has crashed in such a way that it's not trying to display anything."
Would it be possible to explain this to me, in what way could the pc crash with this problem? It's not trying to display anything, so is it my videocard or something else?
Regards
18-May-2012