AVGUI.exe consumes all available CPU cycles even when inactive

Hello Mike,
Let's have a look at it together.
Please share the screenshot of your CPU usage page and the version of AVG you have installed.
Open AVG Internet Security -> Menu -> About -> check its version.
This is still a severe problem by the way. I have an old Windows XP Pro SP3 box which, even though well out of support, I decided could still use some virus protection. I used AVG many years ago so gave it a go, and was pleasantly surprised when it installed fine on XP through the web installer. Everything is fine when I log into my administrator account, but when I log out of that and go back to my standard user account, AVGUI.exe starts consuming 100% of the CPU, rendering the system unusable and the core temperature to skyrocket up to 95 degrees C.

I used the main installer from the AVG website and have ended up with version 18.8.3071, UI version 1.0.134, and antivirus definitions from today. The copyright notice in the about box dates to 2017 so I guess the installer uses an old build if it detects Windows XP, and I found this page suggesting the same thing: https://www.avg.com/en-gb/windows-xp-antivirus#pc

Unfortunately, since this problem is so severe, it seems like AVG isn't actually usable any more for legacy Windows XP machines despite their claims - I doubt it will ever be fixed.

The accepted answer in this forum thread is not correct - there's a huge distinction between a process running and it consuming 100% of the CPU. As a software engineer myself it just looks broken.

The script-based AVGUI.EXE is always active, consuming all available CPU cycles even when the UI is not active.

With AVG installed, a differential backup which took 6 minutes now takes 45 minutes to complete.

No device or directory scanning was scheduled nor active.

For common x86 architectures, suggest implementing a native machine-based language for Windows event messaging rather than relying on the Microsoft .NET Framework interpreter.

Is the secret to AVG's success the inability of its users to run programs?

Intel Pentium 4 CPU 2.40 GHz 1.5 GB of RAM

This is still a severe problem by the way. I have an old Windows XP Pro SP3 box which, even though well out of support, I decided could still use some virus protection. I used AVG many years ago so gave it a go, and was pleasantly surprised when it installed fine on XP through the web installer. Everything is fine when I log into my administrator account, but when I log out of that and go back to my standard user account, AVGUI.exe starts consuming 100% of the CPU, rendering the system unusable and the core temperature to skyrocket up to 95 degrees C.

I used the main installer from the AVG website and have ended up with version 18.8.3071, UI version 1.0.134, and antivirus definitions from today. The copyright notice in the about box dates to 2017 so I guess the installer uses an old build if it detects Windows XP, and I found this page suggesting the same thing: https://www.avg.com/en-gb/windows-xp-antivirus#pc

Unfortunately, since this problem is so severe, it seems like AVG isn't actually usable any more for legacy Windows XP machines despite their claims - I doubt it will ever be fixed.

The accepted answer in this forum thread is not correct - there's a huge distinction between a process running and it consuming 100% of the CPU. As a software engineer myself it just looks broken.

On an Intel Pentium 4 CPU 2.40 GHz 1.5 GB of RAM, AVGUI.exe uses all available CPU when no user interface is requested, no scans are active or scheduled, and no applications of anykind are running.

Competitor's Internet Security performs background scans and virus updates without exhausting the CPU.

I had to use Safe Mode to unistall AVG.

AVGUI useless on an Intel Pentium 4 CPU 2.40 GHz 1.5 GB of RAM.

Windows XP, though all O/S would benefit from a divorce between GUI and other low level methods.

The GUI should not appear in the task list with a non-trivial CPU usage unless the user has requested that interface.

McAfee's has a very slow GUI application under XP also, however, internal methods don't use the slow, interpreted .NET compiled script.

To unistall AVG from my XP computer, I had to log in as Administrator in Safe Mode.

This isn't the experience we want you to have, Mike. 
If you've used AVG Clear to uninstall the program & if you reconsider, we'd suggest you to reinstall AVG & check if it consumes the same amount of CPU usage. 
Please visit this link to download the appropriate setup file of AVG for Windows XP.

Hello Mike,
Let's have a look at it together.
Please share the screenshot of your CPU usage page and the version of AVG you have installed.
Open AVG Internet Security -> Menu -> About -> check its version.

Hello Andrew.
Firstly, this is a very old post and we'd recommend you to write your own post if any help required.
Regarding the issue, since Microsoft has ended support for Windows XP, latest versions of AVG software is not compatible with Windows XP.
However, if you use Windows XP SP3, you can install and older version (18.8) with latest virus definitions.
This will protect your PC from latest threats but the latest features and program updates are not installed.
Make sure you do not have any other antivirus or firewall software installed on your PC.
Then uninstall AVG and install again to verify the CPU usage issue.

Mike, may I ask you the operating system you are using like Windows 7, Windows 8 or Windows 10?  

This will help us to proceed further. Thank you!

Mike, AVG services will always run in the background to actively protect your PC from virus and hacker attacks. The AVGUI.exe process needs to run for the other services to run properly.