No signal input

That message is being generated by your monitor. It is telling you that there is no signal coming from your video card and PC. You would get the same message if you disconnected the video cable.

So what is going on with your video card? That is the question.

The fact that it eventually comes on is curious. That suggests to me that there is a driver error or driver conflict going on and it is taking 20 minutes for Windows to resolve it. But it could be several other things too.

Is there any other information you can give us regarding the behavior. Any error messages? Problem devices in Device Manager? Any other unusual behaviors?

Let us know.

First, test the monitor on another, know working, computer. Make sure the problem does not follow the monitor.

If the monitor tests fine, then I would recommend trying a clean installation of the video drivers.

• Go to the ATI or nVidia website and download the most current known good driver and save it to an easy to find location.
• Now go into Windows Explorer and in the C: drive find the nVidia or Program Files > ATI folder (inside will be Drivers > your driver version) and delete it (the whole folder).
• Go into Start > Control Panel > Remove a Program and uninstall all programs for the video card. For nVidia, do PhysX and Stereoscopic 3D first, then the driver. The control panel will uninstall with the driver. For ATI, select “ATI Catalyst Install Manager” and click on “Change”, then “Uninstall All Components”.
  
• Restart the computer.
• When it reaches the desktop Windows will find new hardware and will install it's own WDDM1.1 driver. Let it. You will be asked to restart. Do it.
• Once back on the desktop you can now install the nVidia/ATI driver package for your card.

If reinstalling the drivers does not clear up the symptom then you may have to start thinking about a defective video card.