I've been trying to install .NET Framework 3.5 on a Windows 8.1 computer without any luck. I tried the basic approach of downloading and installing it from MSDN which failed saying it couldn't connect to the internet.

Then I tried dism as explained in several forum posts:

Dism.exe /Online /Enable-Feature /FeatureName:NetFX3 /All /Source:E:\sources\sxs /LimitAccess

but I keep getting an error:

Error: 0x800f081f
The source files could not be found.

and in the log file I found something weird:

Encountered an unknown option "source" with value "E:\sources\sxs"

I also tried copying the sxs folder to c:\temp\sxs and putting this in the source.

According to this blog post it isn't possible to install .NET 3.5 after a language pack has been installed. Is there any known workaround to this by now? Danish is the only available language. I'm not able to switch back to English or even install an English language pack.

  • are you using proxy for internet? – MAKZ Feb 13 '14 at 10:43

There is a known way to do it. You have 2 ways. If you have a DVD with the second language that you have installed, copy the SxS folder from this 2nd DVD to the folder c:\temp\sxs or downlaod the MUI pack of the language that you installed and extract the LP.cab also in the folder c:\temp\sxs with expand.exe which is part of Windows.

Now you can run the DISM command and Windows will find the files for both languages.

  • the first method you provide is exactly what i did, there's only danish on this system and on the dvd i got the sxs folder from. i don't understand the second method you suggest. – user19161 Feb 13 '14 at 8:00
  • no, you must copy the SxS folder from an ISO of the language that you installed! Not the DVD that you used for install Windows 8. What was the language that you installed and which one did you added? Do you use a 32Bit or 64Bit Windows 8? – magicandre1981 Feb 13 '14 at 8:02
  • i didn't install any second langauge. the system has been in danish per default (from the installation dvd probably), and i suspect i have to change it to english to be able to install .net 3.5 – user19161 Feb 13 '14 at 8:05
  • upload the CBS.log so that I can see which files are missing. – magicandre1981 Feb 13 '14 at 8:09
  • the log shows the DA-DK language files are missing. Are you sure that the DVD is danish? Look into the sxs folder for da-dk folder names. – magicandre1981 Feb 13 '14 at 19:03

I had the same problem. The standard solution didn`t work.

After I removed every .NET based security update, it was possible to install the .NET Framework 3.5. Afterwards I reinstalled the removed updates again, and everything was fine.

  • 2
    I ran into this problem, too. Specifically, I removed KB2966826 and KB2966828 security patches. From this link: Can't install .NET Framework 3.5 on a Windows 8.1 computer.. – LarsTech Sep 7 '14 at 12:27
  • @LarsTech this fixed it for me. After uninstalling those 2 KB's, I was able to install the framework using the Add Windows Features screen in the control panel – wwarren Sep 9 '14 at 0:43

Found link that identifies two Windows Updates as the problem if DISM and the offline installer do not work. Uninstall KB2966826 and KB2966828, then try installing 3.5 from programs and features. It worked for me.

By Chris Wardario

protected by Community Oct 8 '14 at 16:50

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