Why did I get error 0x80003940?

Windows Update continous fails to search for Updates or cannot install them. The source of this problem could be various things as
> Windows Registry
> Windows Filesystem
> Internet access

> Windows Update service
> File corruption
> Misconfiguration
> Adware
> Virus and Malware

How to fix Windows Update error 0x80003940?

However, if you’re technically savvy, you can try the steps below:

1. Click Start and start typing on your keyboard for "services.msc"

2. In your search results "services.msc" should show up. Open it with a click.
3. A new windows will open containing all Windows services on your system.

4. Search for "Windows Update"
5. Right-click the "Windows Update" and then click Stop.

We will now clean the Windows Update temporary cache folder:
1. Hold your windows-key pressed and hit "R" key simultanous.
2. A small new windows will appear.
3. Type %windir%\SoftwareDistribution\DataStore in this new window and click OK.
4. This will open Windows Explorer on the correct location.
5. Delete all contents of this folder. (Hint: Use Ctrl + A to select all files and folders)

Now we will start the Windows Update Service again:
1. Switch back to the windows Services.
2. Locate Windows Update.
3. Right-click on it and choose Start.


If the problem still persists, you can run the System File Checker (SFC) utility. This handy in-built tool will check your filesystem.
1. Click Start and start typing on your keyboard for "cmd".
2. In your search results cmd should show up with an black icon.
3. Right-click it and select Run as administrator.
4. If you are prompted for the admin password, enter the password and click OK.
5. A new completely black windwos will open. You can type commands directly into this window.
6. Type sfc/scannow and press Enter.
7. This process will take a long time. You can minimize this black windows and work on.
Come back to the black window after a time and check if the process finished.
As soon as the SFC process finished, restart your computer. After the restart you search for Updates again.


You are still facing the same issue?

1. Restart your computer.

Next thing is to clean Windows Update download path. These steps are only for expirienced user! If you mess up your computer with Regedit, you could loose your files! Take care or use a professional tool to investiagte your computer.
1. Hold your windows-key pressed and hit "R" key simultanous.
2. A small new windows will appear.
3. Type regedit in this new windows and hit Enter.
4. In the new windows you have a navigation on the left side. Use it to navigate to
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate
5. Once you found it, search for WUServer and WIStatusServer in the right hand pane.
6. If they are not listet we cannot clean the download path. Othwerwise delete both.
7. Restart your computer.

Try to search for new Updates again.
You are still facing this issue? I think this is not an usual problem and your computer should be checked by professional.
Try to look for a solution here or search further in the search box below.



Advanced information

The following Windows verisons are affected by this error:
> Windows Vista
> Windows 7
> Windows 8
> Windows 8.1
> Windows 10
> Windows 10 Redstone 2
> Windows 10 Creators Update
> Windows Server 2008 R2
> Windows Server 2012
> Windows Server 2016
0x80000000 oldVal1 mode1Res1 stages 00000 chip scan values 0x03 card type Lists Mailing 80867190 0x80003950 ROMEXEC kernelotext 8086 Xfree Server 13072005 dmarre Super Micro Code thumbmainreturn Thumb 0000 LaLinux xpertxfree86org XF86 problem mode addr pciopen1 SATA forumlissyarasu mode1res0x80000000 pcicfgcheck pciopen1a port 0x0cf8 15ad Probing config version ACPI SourceForge console XWindow framebuffer using method extremely slow Motion lockModeIS Silicon 00000000 Aery32LUFA 80867194 Debian 29072001 Databases Design Everything deadlock dBforums lasttranstarted20100712T183957160 XDES0x80003940 transactionnameSELECT waittime2398 ownerId1721972 working textpmwaitforclk0ready srcASFavr32driverspmpmo pmenableclk0nowait master Ripagood Read 0x80003858 Prjectmap pmwaitforclk0ready EasyARM2200KEILuCOS252rar 0xd4 cprogram 29072012 build GitHub toolchainbinlibgccavr32443avr32libucr2libcalibacallatexito EVK1105ET024006DHUEXAMPLE2map toolsavr files x86atmelavr