How to Fix: Windows Upgrade Assistant Stuck at 99%

Dennis Faas's picture

Infopackets Reader David L. writes:

" Dear Dennis,

I read your article about still being able to upgrade to free Windows 10 even after the deadline. I've downloaded the Windows10Upgrade24074.exe file and ran it; however, it takes over an hour to download the files and then the Windows 10 upgrade assistant gets stuck at 99% complete. I have tried doing this 5 times and the upgrade assistant keeps getting stuck at 99%. I've left it for an entire day and - as you may have guessed - Windows 10 upgrade assistant is still stuck at 99% complete. What can I do to get the free Windows 10 upgrade, and/or how can I get passed 99% complete? "

My response:

I have not had this problem before so I asked David if I could connect to his system to have a look. He agreed and sure enough, the Windows Update Assistant remained stuck at 99%. At this point, I pressed CTRL + ALT + DEL to bring up Task Manager, where I saw the svchost.exe (service host) process running steady at 25% CPU usage non-stop. I also noticed that svhost.exe process was eating up 62 megabytes of memory and did not fluctuate.

Tip: when you see a process that has high CPU usage and memory usage that does not fluctuate, it's a safe bet that the process is stuck. This is especially true if you've waited for a ridiculous amount of time for something to complete, as in David's case - an entire day - and nothing changes.

How to Fix: Windows Upgrade Assistant Stuck at 99%

At this point I decided to research the issue online, and came across a number of posts with seemingly no definitive answer to the problem. I decided to investigate the svchost.exe process a bit further, as I knew that this process must be related to the Windows Update Assistant.

I knew this was true because whenever I quit the Windows Update Assistant, the svchost.exe process also went away. So, I decided to open up Task Manager once again, then right clicked on the stuck svchost.exe process, then selected "Go to services". As I suspected, one of the services attached to the svchost.exe was Windows Update - so that suggested to me that there was a very, very good chance that the Windows Update Assistant was conflicting with the Windows Update Service.

To test my theory, I shut down the Windows Update service and noticed that the CPU usage on the svchost.exe process dropped immediately. Unfortunately, that didn't help to progress the Windows Update Assistant past the 99% point. I then decided to close the Windows Update Assistant, then shut down the Windows Update service once again, then renamed the SoftwareDistribution directory (which is where Windows Update downloads its files), which then effectively reset Windows Update. Sometimes when you reset the SoftwareDistribution directory in this manner, it clears out a corrupted Windows Update service. I then re-ran the Windows Upgrade Assistant, and it finally got passed the 99% point.

Here's how I fixed the 'Windows Upgrade Assistant Stuck at 99%' problem, in detail:

  1. There are some preliminary issues to take care of before we get started. First, close the Windows Update Assistant if it's currently running on your system. Second, backup your system using a disk image if you haven't already - this is important. If Windows 10 fails to install properly, your system may not boot after the upgrade. I've already had people email me and tell me the Windows 10 upgrade messed up their system something fierce, so a disk image backup is the best insurance you can have. If you don't know how to make a disk image backup, you can contact me for support; simply refer to the link near bottom of article.
  2. Assuming you've created a disk image backup, it's time to open up an administrative command prompt. To so so: click Start, then type in "cmd" (no quotes); wait for "CMD.EXE" or "Command Prompt" to appear in the list, then right click it and select "Run as administrator".
  3. Next, use your mouse to highlight the text below:

    net stop wuauserv
    cd %systemroot%
    rename SoftwareDistribution SoftwareDistribution.old
    net start wuauserv
    echo this is a dummy line
  4. Right click over the highlighted text above, then select "Copy" from the dialogue menu. Go to the black command prompt you opened in Step #2, then right click in the middle of the window and select "Paste". The text you copied in Step #3 should now be output on the command line.
  5. Now, run the Windows Update Assistant again. Note: if you haven't already downloaded the Windows 10 Upgrade assistant, you can read about it and download it from this article.
  6. Be patient as the files download and extract onto your system. Eventually, the Windows Upgrade Assistant should pass the 99% mark. After that, Windows will restart your PC and begin the Windows 10 installation process. You will have the latest version of Windows 10 when the upgrade is complete (which is currently the Windows 10 Anniversary Update, or build number 14933).

I hope that helps.

Additional 1-on-1 Support: From Dennis

If you don't know how to make a disk image backup of your system, or if you're still having issues with the Windows Update Assistant being stuck at 99%, I can help using my remote desktop service. Simply contact me briefly describing your message and I'll get back to you as soon as I can.

Got a Computer Question or Problem? Ask Dennis!

I need more computer questions. If you have a computer question - or even a computer problem that needs fixing - please email me with your question so that I can write more articles like this one. I can't promise I'll respond to all the messages I receive (depending on the volume), but I'll do my best.

About the author: Dennis Faas is the owner and operator of With over 30 years of computing experience, Dennis' areas of expertise are a broad range and include PC hardware, Microsoft Windows, Linux, network administration, and virtualization. Dennis holds a Bachelors degree in Computer Science (1999) and has authored 6 books on the topics of MS Windows and PC Security. If you like the advice you received on this page, please up-vote / Like this page and share it with friends. For technical support inquiries, Dennis can be reached via Live chat online this site using the Zopim Chat service (currently located at the bottom left of the screen); optionally, you can contact Dennis through the website contact form.

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lepitbull's picture

Hi Dennis,

Great posts for my Windows 10, Pearls of Wisdom...

My Question: Does the step 3 work on Failed Tuesday updates for August 2016 ? I want to give my Vista Business (32 bit system with Service Pack 2) to my nephew. But when I checked for the August updates, they did not work and did not install. MS forums did not help either. Even 'PA Bear' was stumped.


P.S. I know, I know vista is old and Outdated but it is supposed be OK and updated until May 2017.

Dennis Faas's picture

Yes, Step #3 may work to resolve windows update issues - however, you should refer to my full article on How to Fix: Windows Update Won't Update, which explains everything you need to know, step by step to fix that particular problem.