AvastSvc.exe frequently spiking to 100% CPU usage, even when idle

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I'd be glad to do a dump for you if I knew what "Task Explorer" is... please explain...

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UPDATE: xperf does not run on Windows XP, so that's not an option for me.

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Using Process Explorer (procexp.exe) from SysInternals, I created AvastUI Minidump.dmp and AvastUI Full Dump.dmp, zipped them into the folder Dumps of avastui.zip, and sent it per PK's instructions to the Avast Team FTP server. The upload to the incoming directory was apparently successful.

Since my issue is with avastui rather than with avastsvc, I posted this message to Topic: AvastUI.exe * 32 always uses 25% of cpu's resources. There is a third topic, Topic: AvastUI.exe using 99% CPU, to which I have not posted because I didn't see it first... 

Thanks for your attention!

[bounty]

Hello
Windows XP SP3
I also had AvastUI using 99~100% of CPU, sometimes never, sometimes forever, sometimes for a period. Prevents some programs (including Winword 97) working. Creates as many problems as the virus's we are trying to protect against.
Avast recommendation is for version 18.8.2356. NO WAYS! - someone at Avast has missed something.
Changing back to version 17.9.2322 has completely cured Avast's messing. You have of course then to set Program update to manual to prevent auto updating.
This version is still available on the internet but apparently not from Avast themselves. You need an OFFline version otherwise you get 18.8 again.
Hoping this prevents users battling like I did. Cheers

[rocksteady]

This thread seems to have morphed from CPU spikes due to avastsvc.exe to CPU spikes on WinXP due to avastui.exe.

CPU hogging on WinXP has been reported many times before with 18.8.2356.
Including myself here due to avastui.exe:
https://forum.avast.com/index.php?topic=220639.msg1549868#msg1549868
Also due to avastsvc.exe on WinXP.
https://forum.avast.com/index.php?topic=220639.msg1484900#msg1484900

I followed advice from DavidR, removed 18.8 (the last avast version for XP) and instead clean installed earlier version 18.5.2342.
Note: also need to turn off automatic-updates, otherwise you wll be updated again to 18.8.

Avast 18.5.2342 does not seem to cause the same avastui.exe CPU spikes on WinXP as 18.8 started doing from 6/2020 in my case.

Edit: to include ref to CPU hogging on WinXP due to avastsvc.exe as well as avastui.exe.