Windows 10 Taskbar preview stopped working

Question

I've got a new GPU today and suddenly the taskbar previews stopped working. Here is how it looks like now:

However it still works fine if I only have 1 window opened. If the same program has 2 or more windows open the preview doesn't work and shows up as on the first screenshot.

Here is the proof that it works fine with only 1 window opened.

Is there any way to fix it? It's not just for steam. If I open multiple explorer windows the preview stops working but with only 1 window it works fine.

The OS is Win10. The new GPU I've got is GTX 1080 if that's of any difference On my old 970 the preview used to work fine even with multiple windows open.

Solution

It's possible that the NumThumbnails registry value is set to 1. What it does is if you open more than one instance of the program, it stacks the items instead of showing the thumb images.

Start Regedit.exe and go to the following registry key:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Taskband

Delete the NumThumbnails value

Exit Regedit.exe, logoff and login back.

(via Increase Taskbar Thumbnail Preview Size in Windows 7, 8 and 10)

Comments

[Ramhound]

We need more information.

[keklord]

I thought I had covered most of the useful info. The OS is Win10. The new GPU I've got is GTX 1080 if that's of any difference On my old 970 the preview used to work fine even with multiple windows open.

[Ramhound]

You didn't indicate much of anything in the original revision. You have installed the current Nvidia drivers, since your previous drivers, are not compatible with it?

[keklord]

I didn't have to reinstall the drivers they were compatible with the new card as well. However I still did a clean reinstall and it didn't seem to change anything

[keklord]

Thanks a lot this worked! Any idea why did this value change by itself? Edit: I have also noticed that my desktop icons rearranged themselves after I installed the new card too

[w32sh]

Did you remember running a 3rd party tweaker or tuner program lately? Or perhaps the GPU software added the entry.

[keklord]

That seems quite likely actually. Even though the desktop shortcuts rearranged themselves before I actually installed the new tuner program I assume it is because the screen resolution changed upon inserting a new card. As for thumbnails, I did install a GPU Tweaker app from Asus. Perhaps it messed with it

[w32sh]

Wow. That's interesting! Will keep that point (GPU tweaker) in mind. It's probably trying to free up your video memory.

[keklord]

Yep, confirmed. I've just tried to do "Boost" in the Tweaker program again and upon restart the thumbnails disappeared and I had to do what you described in your answer again to get them back.