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Desktop and Taskbar Icons Flashing, Explorer.exe CPU is high
Date Added: 6/26/2020

SYMPTOMS:
Desktop and taskbar icons flash 5-10 times per minute. Explorer.exe CPU usage bounces around, but is generally around 40-50%. Killing processes and rebooting computer does not help. No errors in event viewer.

CAUSE:
Explorer is trying to load file previews and failing, and keeps retrying.

DID NOT FIX THE PROBLEM FOR ME:
ccleaner, deleting temp files, uninstalling various programs, turning off startup of most non-Microsoft things via SysInternals Autoruns, deleting iconcache.db and thumbcache files, DISM, SFC.

ACTUAL FIX:
Figure out which preview is causing the problem and disable it. In my case, it was PDF files
Here's how to figure it out:

1) Optionally, install Desktop Restore and save the position of the user's desktop icons. Afterward, you can use Desktop Restore to reload their positions so the user doesn't get annoying that all their icon positions are reset.

2) Open Task Manager, go to the Details tab, and watch the explorer.exe. The CPU should be high right now.

3) Create a new folder on the user's desktop called "icons" (or any name you want)

4) Move all the user's icons from their desktop into the new "icons" folder

5) Close the icons folder and all other explorer folders. You should see no icons on the user's desktop except the Windows ones (trash can, This PC, etc) and the "icons" folder you created.

5) Look at Task Manager and see if explorer.exe is down to 0%. If so, you found the general problem. Opening the icons folder will make explorer just back up to 50% and closing the icons folder will make explorer immediately go back down to 0%. If you still have high explorer.exe cpu usage even after doing this, try removing all the taskbar icons. Or try moving everything from the Desktop/Documents/Downloads and other special folders into a generic folder, like C:\UserFiles\*

6) Assuming the last step fixed explorer.exe, now you have to narrow down which file type specifically causes the problem.

7) Move a group of files from the icons folder back onto the desktop, one file type at a time, then close the icons folder after each group. Watch explorer.exe in Task Manager and when you see that it remains high at 50% even after closing the icons folder, that means the last group you moved to the desktop is the culprit.

8) Next, you need to delete the preview feature for that file type. Open regedit and go to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts.

9) Find the file extension that causes your problem and delete that whole folder, (.pdf in my case). You may have to terminate explorer.exe while you do this, and you may have to add Eull Control permissions to the Everyone group in order to get the whole key deleted.

10) Now, without having to reboot, you should see the problem is 100% solved. You can move all the user's icons back to the desktop and restore their original positions with Desktop Restore. You may want to reassign the default Open With program for that file type. In my case, with pdf files, I reassigned Adobe Reader and the problem did not come back.


credit: https://answers.microsoft.com/en-us/windows/forum/all/desktop-icons-keep-flashing-which-temporarily/70d60e04-9a31-4c55-87c3-0100c98f091a



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