(edited to add this note)

NOTE: I already tried DISM, sfc, the .NET Framework repair tool, turning the .NET Framework features off and on, restoring from a restore point, and resetting the system.

(end edit)

In my home we have Windows 10 Home on two identical HP Envy m6 Notebooks, and by comparing their Windows\Microsoft.NET folders I see that dozens of files are missing from mine.

Five days ago, this message came up when I tried to start Duplicate Cleaner 5:

Duplicate Cleaner Pro 5.19.0

Error starting up Duplicate Cleaner: Could not load file or assembly ‘System.Data, Version =, Culture=neutral, PublicKeyToken=b77a5c561934e089’ or one of its dependencies. The system cannot find the file specified. DataPath=C:\Users\geotalk\AppData\Roaming\DigitalVolcano\DuplicateCleaner

After a lot of searching, wading through a lot of developer talk that's way over my head, and some discussion with the developer, I discovered that these two folders on my computer were empty:

C:\Windows\Microsoft.NET\assembly\GAC_32\System.Data\v4.0_4.0.0.0__b77a5c561934e089 C:\Windows\Microsoft.NET\assembly\GAC_64\System.Data\v4.0_4.0.0.0__b77a5c561934e089

I looked in the same folders on the other computer and found a System.Data dll in both of them. Before I copied them to mine, I tried to use PowerShell, and the same "Could not load" message came up for the same dll, System.Data. After I copied those dll files to my Windows\Microsoft.NET folder, I was able to use PowerShell and Duplicate Cleaner. Since then I haven't had any other problems with Windows or any apps, but I'm concerned about all those files missing from the Windows\Microsoft.NET folder. Before I discovered those two empty folders, I tried DISM, sfc, the .NET Framework repair tool, and turning the .NET Framework features off and on, and none of that restored the missing files. I also tried restoring from a restore point, and resetting the system, but both of those failed.

My problem with PowerShell and Duplicate Cleaner was solved by copying the System.Data dll from the other computer, but I'm concerned about all those other missing files. I don't want to copy them all from the other computer, because I'm afraid it might break something, even it is the same Windows system on two identical computers. I also don't want to do a clean install of Windows if there's any way I can avoid that. It isn't worth all the time and trouble as long as I'm not having any other problems.

Does anyone have any other ideas about how I can restore files that are missing from the Windows\Microsoft.NET folder?

  • .NET Framework 4.8 cannot be reinstalled on Windows 10. You installed a legacy version of .NET Framework, which can be installed alongside .NET Framework 4.8, but none of the described actions can or could have modified your .NET Framework 4.8 installation. Since .NET Framework 4.8 is built-into Windows, the only way to really solve this problem would be to perform an in-place install of Windows
    – Ramhound
    May 19, 2023 at 12:01
  • Looking at my fully functional system, the only file that is supposed to be in that directory is System.Data. I can guarantee with absolute certainty there shouldn't be any other file in that particular folder.
    – Ramhound
    May 19, 2023 at 12:04
  • Thank you. Sorry, part of my post was unclear. I've edited it now to clarify that there are dozens of files missing from my Windows\Microsoft.NET folder. not from the System.Data\v4.0_4.0.0.0__b77a5c561934e089 folders.
    – Lamont
    May 19, 2023 at 14:08
  • Try to restore Windows integrity by running the commands Dism /Online /Cleanup-Image /RestoreHealth and then sfc /scannow.
    – harrymc
    May 19, 2023 at 15:58
  • @harrymc - Did you read the question? The author did that.
    – Ramhound
    May 19, 2023 at 16:30

1 Answer 1


After a few hours of searching and only finding two examples of files missing from the Microsoft.NET folder on the user side, and not finding any examples where the files were restored without a clean install of Windows, I'm thinking that in most cases that would be the only solution, if the files aren't restored by DISM and sfc.

  • 1
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    May 21, 2023 at 11:41

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