Error Code 66A when Updating Microsoft .NET Framework 4 from Windows Update
One of the first thing that I normally do after installing Windows is to disable the automatic Windows Update. Although automatic update is a very convenient way to keep Windows up to date, but I personally do not like Windows or any third party software to automatically do things in background without my knowledge, unless I schedule it to do that. All I need to do is manually check for updates using Windows Update in Control Panel every Patch Tuesday (second Tuesday of each month) as that is when Microsoft releases security patches.
The recent Patch Tuesday released 2 updates and 1 security update for Microsoft .NET Framework 4 with a couple of other updates for Windows. All updates installed without problems except the 3 updates for .NET Framework 4, failing with the error code 66A (Windows Update encountered an unknown error). I tried to install one by one but still no luck.
At first I wanted to reset the Windows Update components using the official Microsoft Fix it 50202 tool but after thinking for a while, this error code 66A should have nothing to do with a broken Windows Update since other updates were able to install except for .NET Framework 4.
My guess is that probably Microsoft .NET Framework 4 has somehow got corrupted and needs to be reinstalled. Instead of uninstall and reinstall Microsoft .NET Framework 4, I should try the repair option first. Go to Control Panel > Programs and Features > select Microsoft .NET Framework 4 Client Profile from the list and click on the Uninstall/Change button. The Microsoft .NET Framework 4 Client Profile Maintenance window will open and select the “Repair .NET Framework 4 Client Profile to its original state”. Click next and follow the on-screen instruction.
After finished repairing .NET Framework 4, I went to Windows Update again and try to install the 2 updates and 1 security update. This time Windows Update reports “The updates were successfully installed” with a checkmark which means the repair fixed the problem and allowed the updates to be installed. I have no idea when or how did the Microsoft .NET Framework 4 got corrupted in the first place.
Perfect. It works! Finally! Thx!
Wow. It works. Thank you
Thanks for this.. Problem solved
Excellent, thank you
You Fixed my Problem!! Thanks a Lot
Update Failed 4 times since last night Code 66a
Microsoft was USELESS – as usual to fix it’s own problem
2018-08 Security and Quality Rollup for .NET Framework 3.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2 for Windows 7 (KB4345590)
Installation date: 8/15/2018 6:14 AM
Installation status: Successful
Update type: Important
A security issue has been identified in a Microsoft software product that could affect your system. You can help protect your system by installing this update from Microsoft. For a complete listing of the issues that are included in this update, see the associated Microsoft Knowledge Base article. After you install this update, you may have to restart your system.
More information:
support.microsoft.com/kb/4345590
Thanks, this solved my problem.
Very helpful, thanks so much!!
Thank you. This is all over our domain. I must have had update kb3037578 fail on over 50+ PCs. Repair does not work, uninstall and then reinstall usually cures it.
Thanks for this information. My .NET Updates were successfully installed. :)
thanks man!finally solved my “error 66a” problem. great website.
Thank you for the information and I followed your suggestions to completion and had come to find out that some how my .NET Framework 4 had been uninstalled some how which was stopping me from completing this recent Windows Update. I went a step further and sought out the most recent version of .NET Framework 4 and downloaded from here this Windows site version 4.5 after a few snags in the installation where it couldn’t locate a couple of files but searching for them i was able to give the installation the proper file folder to complete. After the installation was finished went to windows update again and it was current with a big green check mark and shield. Thanks again for the insight or i would have never been able to fix this issue
To fix error code 66a easily, you must go for automatic fix tool which help you to get rid of this Windows update error completely.
I did the same thing and works great!
Urg! I haven’t updated my Win 7 since last year as I wanted to format the system well its nearly a year still haven’t got my lazy ass self to format the pc. I decided to update windows getting 3-4 Framework 4 updates failed while 40+ others passed. I did the same thing repair then installed failed, then tried using their cleanup tool then reinstalled Frameworks 4, then update it 3-4 of the updates finally passed except 1! Not sure what to do to get it installed.
Thank´s Raymond. Very good article.
I haven´t that problem myself, but good to know anyway…
Like You, I also keep updates on manually, cause I want to know, what´s happening and wan´t to select, what updates to install.
Question: Is there any simple solution to “averige users”, how to control what updates to accept to install from windows updates..?
Question is kind of silly, but I have noticed that for example Microsoft Office updates, offered for download even if you don´t have example outlook in your machine. I have no problems with those myself, but I allways worryi´n my “client´s” machines.. So much updates, wich are no need to install or use….
This my typing is probably unnecessary waste of time for everybody, but I just wondering here…
Thanks Raymond. Happily I’m one of the lucky ones who installed this update without errors.
This is a common problem with NET framework. Quickbooks relies on this framework to work and every time it gets corrupted or messed up Quickbooks freezes or doesn’t work properly.
I’m sticking with 3.5…i read an article in Windows secret saying that .net 4 isn’t stable. Not sure whether the update supposed to fix that or not.
Thanks, Raymond, for the article. I, for one, already knew about it, but I’m sure others benefitted.
My reason for posting, though, is to give your readers the benefit of something I’ve learned about the .NET framework which I believe that everyone needs to know, to wit…
Never, EVER uninstall any .NET framework components. Always repair or, if possible, re-install over the top of an existing installation. But never, trust me on this, uninstall.
Many who hate Microsoft and Windows decry the .NET framework… especially those who prefer Linux. However, .NET, in the main, is little different from what Java does… and Java’s the darling of the Linux world. So six of one is a half dozen of the other.
The thing is, though, that it’s possible to completely remove Java without damaging Windows. So score one for the Linux world, there…
…because it is NOT possible to uninstall .NET (except maybe old version 1 or 1.1, I suppose) without somehow screwing-up Windows.
Trust me on this.
The one and only time I’ve needed to wipe the drive on this notebook that I’m now using (and I’ve been using it since 2007), and restore it to the way it came from the factory (and then reinstall everything and restore my data from a backup) was when I tried to remove anything related to .NET from my machine.
Oy. What a freakin’ nightmare!
I even found the web site of a guy who helped develop .NET, and who still works for Microsoft in that department, and who, on his site, provides a wealth of .NET-related information and support…
…and nothing on his site (and, believe me, there was a TON of good stuff there) helped. Nothing.
I finally convinced him to remote into my machine and try a few tricks himself.
Nothing worked. Even HE was stumped. When one of the guys who DEVELOPED .NET can’t figure it out, that’s really saying something.
I subsequently further researched it and found lots of people who tried to remove (uninstall) some aspect of the .NET framework and they had similar horror stories to tell.
The .NET framework, starting a little bit with version 2, but ESPECIALLY with version 3, is so complex and, frankly, screwed-up, that once it’s installed on one’s Windows machine, it becomes so much a part of the core of Windows, itself, that it can never really be properly removed…
…and if one tries, it just screws-up Windows so that it can’t be properly re-installed.
Even repairing .NET components can be dangerous (though doing that is at least better than trying to uninstall) sometimes.
I’m happy that repairing worked for you, Raymond. But I’m glad that you didn’t end-up suggesting to anyone that they should remove it and re-install it. As I was reading your article, I was thinking to myself, “ohgod… Raymond… you’re not gonna’ advise the readers to uninstall it, are you?… ohgod…”
I’m not saying that it wouldn’t have worked in your case. As with most things Windows-related, what fails for one user may well work just fine for another. That, after all, is where the often-used phrase “your mileage may vary,” when applied to computers (where “mileage” isn’t an actual issue) came from in the first place.
Just, please, everyone who’s reading this (and, Raymond, you’d do well to both add a note about this to your article, and also keep this in mind for future .NET articles): Be very careful when it comes to fiddling around with the .NET framework, just generally. Unless you’re developing in it, never install the full version, or the SDK or anything like that. Regular end-users should always just install the redistributables (and in the proper order, thankyouverymuch), and then NEVER try to uninstall them, no matter what. Instead, just always allow Windows Update to update them. Never try to circumvent or hid an update… just don’t fight it. And, as Raymond just demonstrated in this article, repair .NET-related stuff only when necessary if an update fails; but NEVER uninstall any part of it.
Never!!!!!!!
Just tryin’ to help.
Keep-up the good work!
Peace.
_______________________________
Gregg L. DesElms
Napa, California USA
[email protected]
Brilliant! I was having trouble fixing this. Thank you!
Your article is very informative. thank u!
.net Framework 4 rendered 2 of my programs unusable. I had to remove it. Now I only install .net Framework if the program requires it. Less bloat if not needed is always better.
Mine also failed the first time. After rebooting, the .net’s installed OK.
My problem was different being that I had 15 critical updates that were ready for download as I keep my pc on auto updates, but do not install, as I wish to see what Microsoft is installing. The 15 critical updates installed, and the 3 optional Net Framework 4 would not download.
Usually I go to the “Tech Microsoft”, type in the #’s related to the updates, computer searches and finds all related updates and I install the updates manual based on my pc. (Then I run “Belarc Advisor”, to make sure that all updates are insalled). If not I run again manual.
same problem but I called ms help and had to uninstall my net 4 and took hrs on phone and hrs updating . so wish seen your fix first. or least told to try by ms help.
thanks great tip for those still error code.
thanks for your help.
I GOT THE SAME PROBLEM.
BUT I HAD RESOLVED IT IN ANOTHER WAY(may be not better than yours).
I WENT TO FOLDER “C:\Windows\SoftwareDistribution\Download”
FOUND FILE OF SAME AS THAT OF UPDATE SIZE FILES.
I COPIED THOSE TWO BIG FILES(~27MB & ~34MB) TO ANOTHER LOCATION.
AFTER THAT I ADDED “.exe” EXTENSION TO THOSE FILES.
AND INSTALLED THEM.
AFTER THAT I RUN WINDOWS UPDATE.
AND THEY GOT INSTALLED WITHIN A MINUTE.
Nice
thanks , I was facing same problem .
Thanks Ray. I was getting very annoyed on that error. Your article fixed it for me.
Good one Ray………..
This happened to me as well, and I did that same thing to resolve the problem. I never figured out the cause and shrugged it off.