When I display 'All Tasks' in the BOINC Manager I get this message against some of the tasks, that I would normally expect to be running using the GPU, as they used to. I have not changed anything. I am running Windows 10 on my PC.

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Is it possible that Windows 10 installed new drivers for the videocard?
Try to run dxdiag.exe from the Windows Search and see what version of drivers it says are installed.

Anything above 15.7.1 has no OpenCL support anymore for your videocard's GPU, so if you do find you have a later driver than that, you'll have to uninstall the newest drivers, and install previous ones with a maximum of 15.7.1

You can also tell Windows to stop auto-upgrading your drivers: http://winsupersite.com/windows-10/stop-automatic-driver-updates-windows-10, best do so before they get replaced yet again.

Drivers can normally be uninstalled through Programs and Features, but it may be needed under Windows 10 to uninstall them through Device Manager. Or you can use Display driver Uninstaller to get rid of the previous drivers (and a lot of junk that gets left behind otherwise).

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Ageless, thank you for your reply.
The system reports that the latest driver update was on the 30th January 2016, and the current version is: 15.201.1151.1008. I presume therefore that the answer to my problem lies elsewhere as the GPU was not missing until a couple of days ago.....

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If you say it worked fine until a couple of days ago... it may be it's a message for something else.
Looking at your task list you got three SETI@home v8 v8.00 (opencl_ati5_cat132)
windows_intelx86 in today. So whatever it was, it seems to be fixed.

A missing GPU is in 90% of the cases to do with the drivers.
The other 10% range for installing BOINC as a service, the GPU being really broken and possible broken motherboards.

Now the latter two are easily dismissed if you use the GPU for your monitor as well, see things on it and those things aren't distorted or full of artifacts.

Which leaves BOINC as a service, which you can see in the Event Log (CTRL+SHIFT+E) and the message somewhere close to the top that BOINC is "running as a service". If that's there, uninstall, reinstall and in the third screen in the installer click Advanced, then uncheck "Service Install" before continuing the installation.

But if that is also not there, it is drivers. Be it that they broke/got corrupted, or anything else.
I see in our ATI/AMD driver cheat sheet that Catalyst 15.7.1 (the absolute maximum for older GPUs) is 15.200.1062.1004, which must mean that your 15.201.1151.1008 is already past that driver and therefore possibly not viable anymore.

For the next time you see this message, please post the corresponding part of the messages (from the event log at CTRL+SHIFT+E), and post the BOINC start up messages, first 40 or so lines as well. That gives helpers a lot of information.

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Ageless, thanks once again for your kind attention.
I believe that I have now found the embarrassingly simple reason for the problem. The GPU seems to go missing when I have more than one user ID logged on to the PC at the same time. Usually I am using either my normal id or an Administrator id,and I do not often have both logged on at the same time. If the messsage appears and I then logoff one of the user IDs, normal service resumes.
Problem solved, thanks.

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Ah yes, the remote desktop protocol (which is what's used for fast user switching and for actually logging in on the computer from remote) will also stop using the GPU.

This is because that protocol uses its own Windows driver for videocards, which lacks all the exotic stuff such as OpenCL, OpenGL, CUDA and all that. This to make it compatible with all kinds of videocards.

As soon as you switch back to the original account, the driver installed by that account is used again and presto! GPU found.

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